Numbers as only valid input in edit control

Im having issues with allowing the users only to enter a number in an edit control. I tried using IsDigit(value) but has trouble when the number when negative.

Is there a valid way of allowing the user to only enter numbers but without limiting to positive? I wanted to avoid having a second option they would have to check for negative / positive.

Code:

switch (message)
	{
	case WM_INITDIALOG:
		SetDlgItemInt(hDlg, IDC_XVECTOR, theDoc.hBall.sBallVec.cx, TRUE);
		SetDlgItemInt(hDlg, IDC_YVECTOR, theDoc.hBall.sBallVec.cy, TRUE);
		return TRUE;

	case WM_COMMAND:
		if (LOWORD(wParam) == IDOK) 
		{
			LONG tempX = GetDlgItemInt(hDlg, IDC_XVECTOR, FALSE, TRUE);
			LONG tempY = GetDlgItemInt(hDlg, IDC_YVECTOR, FALSE, TRUE);
			
			if(tempX < -10)
				theDoc.hBall.sBallVec.cx = -10;
			else if(tempX > 10)
				theDoc.hBall.sBallVec.cx = 10;
			else
				theDoc.hBall.sBallVec.cx = tempX;

			if(tempY < -10)
				theDoc.hBall.sBallVec.cy = -10;
			else if(tempY > 10)
				theDoc.hBall.sBallVec.cy = 10;
			else
				theDoc.hBall.sBallVec.cy = tempY;

			EndDialog(hDlg, LOWORD(wParam));
			InvalidateRect(hDlg, NULL, TRUE);
			return TRUE;
		}
		else if(LOWORD(wParam) == IDCANCEL)
		{
			EndDialog(hDlg, LOWORD(wParam));
			return TRUE;
		}
		break;
	}
	return FALSE;

thanks

Have you considered subclassing the edit control to only allow input of 0 thru 9 and the - character?

set its window style to ES_NUMBER

set its window style to ES_NUMBER

Nope, I was thinking more along the lines of this example