petit probleme en c++

bonjour!
je développe actuellement un logiciel en c++ pour piloter un moteur pas à pas.
j'aimerais piloter le moteur par demi pas,en ayant une vitesse reglable(pas trop rapide,pas trop lente!)
g déjà réussi à faire tourner le moteur,les sorties sont bonnes,seulement g un problème avec la consigne de vitesse.
en effet,j'utilise la commande sleep(une valeur)
et je n'arrive pas à arreter le systeme qd j'appuie sur un bouton!
pourriez vous m'aider svp?
je vous remercie d'avance

voici ci dessous un extrait du code source:

for (variableboucle = 10; variableboucle<=consigne; variableboucle++)
{
_outp(0x378,0x1);
Sleep(a);
_outp(0x378,0x5);
Sleep(a);
_outp(0x378,0x4);
Sleep(a);
_outp(0x378,0x6);
Sleep(a);
_outp(0x378,0x2);
Sleep(a);
_outp(0x378,10);
Sleep(a);
_outp(0x378,0x8);
Sleep(a);
_outp(0x378,0x9);
Sleep(a);

}
_outp(0x378,0x0);
}

ca serait bien si on avait les source en entier

-------------------------------
Réponse au message :
-------------------------------

> ca serait bien si on avait les source en entier

le prog a été fait avec visual c++6 .
et voici les sources en entier!

// essai moteur 2Dlg.cpp : implementation file
//

#include "stdafx.h"
#include "essai moteur 2.h"
#include "essai moteur 2Dlg.h"
#include <dos.h>
#include <conio.h>
#include <stdio.h>

#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

/////////////////////////////////////////////////////////////////////////////
// CAboutDlg dialog used for App About

class CAboutDlg : public CDialog
{
public:
CAboutDlg();

// Dialog Data
//{{AFX_DATA(CAboutDlg)
enum { IDD = IDD_ABOUTBOX };
//}}AFX_DATA

// ClassWizard generated virtual function overrides
//{{AFX_VIRTUAL(CAboutDlg)
protected:
virtual void DoDataExchange(CDataExchange* pDX); // DDX/DDV support
//}}AFX_VIRTUAL

// Implementation
protected:
//{{AFX_MSG(CAboutDlg)
//}}AFX_MSG
DECLARE_MESSAGE_MAP()
};

CAboutDlg::CAboutDlg() : CDialog(CAboutDlg::IDD)
{
//{{AFX_DATA_INIT(CAboutDlg)
//}}AFX_DATA_INIT
}

void CAboutDlg::DoDataExchange(CDataExchange* pDX)
{
CDialog::DoDataExchange(pDX);
//{{AFX_DATA_MAP(CAboutDlg)
//}}AFX_DATA_MAP
}

BEGIN_MESSAGE_MAP(CAboutDlg, CDialog)
//{{AFX_MSG_MAP(CAboutDlg)
// No message handlers
//}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CEssaimoteur2Dlg dialog

CEssaimoteur2Dlg::CEssaimoteur2Dlg(CWnd* pParent /*=NULL*/)
: CDialog(CEssaimoteur2Dlg::IDD, pParent)
{
//{{AFX_DATA_INIT(CEssaimoteur2Dlg)
// NOTE: the ClassWizard will add member initialization here
//}}AFX_DATA_INIT
// Note that LoadIcon does not require a subsequent DestroyIcon in Win32
m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);
}

void CEssaimoteur2Dlg::DoDataExchange(CDataExchange* pDX)
{
CDialog::DoDataExchange(pDX);
//{{AFX_DATA_MAP(CEssaimoteur2Dlg)
// NOTE: the ClassWizard will add DDX and DDV calls here
//}}AFX_DATA_MAP
}

BEGIN_MESSAGE_MAP(CEssaimoteur2Dlg, CDialog)
//{{AFX_MSG_MAP(CEssaimoteur2Dlg)
ON_WM_SYSCOMMAND()
ON_WM_PAINT()
ON_WM_QUERYDRAGICON()
ON_BN_CLICKED(IDC_EXIT, OnExit)
ON_BN_CLICKED(IDC_GO, OnGo)
//}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CEssaimoteur2Dlg message handlers

BOOL CEssaimoteur2Dlg::OnInitDialog()
{
CDialog::OnInitDialog();

// Add "About..." menu item to system menu.

// IDM_ABOUTBOX must be in the system command range.
ASSERT((IDM_ABOUTBOX & 0xFFF0) == IDM_ABOUTBOX);
ASSERT(IDM_ABOUTBOX < 0xF000);

CMenu* pSysMenu = GetSystemMenu(FALSE);
if (pSysMenu != NULL)
{
CString strAboutMenu;
strAboutMenu.LoadString(IDS_ABOUTBOX);
if (!strAboutMenu.IsEmpty())
{
pSysMenu->AppendMenu(MF_SEPARATOR);
pSysMenu->AppendMenu(MF_STRING, IDM_ABOUTBOX, strAboutMenu);
}
}

// Set the icon for this dialog. The framework does this automatically
// when the application's main window is not a dialog
SetIcon(m_hIcon, TRUE); // Set big icon
SetIcon(m_hIcon, FALSE); // Set small icon

// TODO: Add extra initialization here

return TRUE; // return TRUE unless you set the focus to a control
}

void CEssaimoteur2Dlg::OnSysCommand(UINT nID, LPARAM lParam)
{
if ((nID & 0xFFF0) == IDM_ABOUTBOX)
{
CAboutDlg dlgAbout;
dlgAbout.DoModal();
}
else
{
CDialog::OnSysCommand(nID, lParam);
}
}

// If you add a minimize button to your dialog, you will need the code below
// to draw the icon. For MFC applications using the document/view model,
// this is automatically done for you by the framework.

void CEssaimoteur2Dlg::OnPaint()
{
if (IsIconic())
{
CPaintDC dc(this); // device context for painting

SendMessage(WM_ICONERASEBKGND, (WPARAM) dc.GetSafeHdc(), 0);

// Center icon in client rectangle
int cxIcon = GetSystemMetrics(SM_CXICON);
int cyIcon = GetSystemMetrics(SM_CYICON);
CRect rect;
GetClientRect(&rect);
int x = (rect.Width() - cxIcon + 1) / 2;
int y = (rect.Height() - cyIcon + 1) / 2;

// Draw the icon
dc.DrawIcon(x, y, m_hIcon);
}
else
{
CDialog::OnPaint();
}
}

// The system calls this to obtain the cursor to display while the user drags
// the minimized window.
HCURSOR CEssaimoteur2Dlg::OnQueryDragIcon()
{
return (HCURSOR) m_hIcon;
}

void CEssaimoteur2Dlg::OnExit()
{
// TODO: Add your control notification handler code here
OnOK();
}

void CEssaimoteur2Dlg::OnGo()
{
int variableboucle = 10;
int a = 200;

for (variableboucle = 10; variableboucle<=25; variableboucle++)
{
_outp(0x378,0x1);
Sleep(a);
_outp(0x378,0x5);
Sleep(a);
_outp(0x378,0x4);
Sleep(a);
_outp(0x378,0x6);
Sleep(a);
_outp(0x378,0x2);
Sleep(a);
_outp(0x378,10);
Sleep(a);
_outp(0x378,0x8);
Sleep(a);
_outp(0x378,0x9);
Sleep(a);

}
_outp(0x378,0x0);
}

merci