Brauche Hilfe (VBA)

Wie kann ich in Excel unter VBA einen Button aktivieren.
Und zwar möchte ich das so haben:
Nach einer bestimmten Bedingung soll der Button automatisch gedrückt
(bestätigt) werden. Wie kann ich dies in VBA tun?
Ich habe es schon mit diesen Varianten ausprobiert:
cmdStopMonitor. = msoButtonSetOK
cmdStopMonitor.Enabled = True
-->funktioniert nicht.

Quellcode:
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Public Sub update()
    ' this updates one row of data and then sets the timer for the
next reading
    Dim timeString As String

    On Error Resume Next
    If continueMonitor Then ' the monitor function is on, set the
timer
        ' set the time for the next reading at 2 seconds
        ' set it first for best accuracy between measurements
        ' Note; setting for less than one second intervals may
        ' prevent the stop button from working
        'intervalString = UserForm1.TextBox1.Text
        If intervalString = "" Then
         intervalString = TextBox1.Text
        End If

        nextTime = Now() + TimeValue("00:00:" + intervalString)

        ' Put the time relative to start time into the column 1
        ' the row is indicated by the global variable 'row'
        ActiveSheet.Cells(row, 1).Select
        Cells(row, 1).Value = Format$(Now() - startTime, "hh:nn:ss")


        If Cells(row, 1).Text = "0" Then ' bad value
                continueMonitor = False
        Else
            ' Call the macro recorded with the toolbar
            If CheckBox1.Value = True Then
             MeasureDCVolts
            End If

            If CheckBox2.Value = True Then
             CurrentDCAmpere
            End If

            ' increment the row one down
            row = row + 1

            ' now set the timer for the next reading
            Application.OnTime nextTime, "sheet1.Update"
            If anzahl_messwerteString = row Then
             'cmdStopMonitor. = msoButtonSetOK
             cmdStopMonitor.Enabled = True
            End If
        End If
    End If
End Sub