Dim start As Single
 
Private Sub Command1_Click()
    Select Case Timer1.Enabled
        Case False
            start = Timer
            Timer1.Enabled = True
        Case True
            Timer1.Enabled = False
    End Select
End Sub
 
Private Sub Form_Load()
    Label1.Caption = "00:00.00"
End Sub
 
Private Sub Timer1_Timer()
    Label1.Caption = Format(Fix((Timer - start)  60), "00:") & _
    Format(Fix((Timer - start) Mod 60), "00:") & _
    Right(Format(Timer - start, ".00"), 2)
End Sub