Dim tmp
Dim test
test = "02:00"
test1 = "04:00"
If Check1.Value = 1 Then
        Text1.Text = Format$(Text1.Text, "HH:mm")
        tmp = CDate(Text1.Text) - CDate(test1)
        Text3.Text = CDate(tmp)
        Text3.Text = Format$(Text3.Text, "HH:mm")
End If
If Check1.Value = 0 Then
        Text1.Text = Format$(Text1.Text, "HH:mm")
        tmp = CDate(Text1.Text) - CDate(test)
        Text3.Text = CDate(tmp)
        Text3.Text = Format$(Text3.Text, "HH:mm")
End If

time1 As String
time2 As String
nMin As Long
 
time1 = "02:00"
time2 = "04:00"
' time2 in Minuten darstellen
nMin = Val(Left$(time2, 2)) * 60 + Val(Mid$(time2, 4))
 
' jetzt die Minuten von time1 abziehen
Debug.Print Format$(DateAdd("n", -nMin, time1), "hh:nn")

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Sub Test()
   Dim Test As Date
   Dim Test1 As Date
 
   Test = "02.02.2016 02:00"
   Test1 = "01.02.2016 04:00"
 
    MsgBox Format(Test - Test1, "HH:MM")
End Sub