jms, as lavolpe said, something like this, this just add / subtract the value while pressing button, just add 2 cmd button, 1 label, 1 timer
Code:
Dim Cnt As Integer, Cmd As Integer

Private Sub Command1_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
If Button = 1 Then
    Cmd = 1
    Timer1.Enabled = True
End If
End Sub

Private Sub Command1_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
If Button = 1 Then
    Timer1.Enabled = False
End If
End Sub

Private Sub Command2_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
If Button = 1 Then
    Cmd = 2
    Timer1.Enabled = True
End If
End Sub

Private Sub Command2_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
If Button = 1 Then
    Timer1.Enabled = False
End If
End Sub

Private Sub Form_Load()
Timer1.Interval = 10
Timer1.Enabled = False
End Sub

Private Sub Timer1_Timer()
If Cmd = 1 Then
    Cnt = Cnt - 1
ElseIf Cmd = 2 Then
    Cnt = Cnt + 1
End If
Label1.Caption = Cnt
End Sub