Dim h, m, s As Integer

Private Sub Command1_Click()
Timer1.Enabled = True
End Sub

Private Sub Command2_Click()
Timer1.Enabled = False
End Sub

Private Sub Command3_Click()
h = 0: m = 0: s = 0
Label1.Caption = "00:00:00"
Timer1.Enabled = False
End Sub

Private Sub Form_Load()
h = 0: m = 0: s = 0
Timer1.Enabled = False
Timer1.Interval = 1000
Label1.Caption = "00:00:00"
End Sub

Private Sub Timer1_Timer()
s = s + 1
If s = 60 Then
s = 0: m = m + 1
End If
If m = 60 Then
m = 0: h = h + 1
End If
t = h & " : " & m & " ; " & s
Label1.Caption = Format(t, "hh:mm:ss")
End Sub