问函数返回MsgBox 10次？

EN

Function TimeValue(FromTime As String, ToTime As String, StartTime As String, StopTime As String, Optional Weekday As String, Optional Daynr As Integer, Optional Holiday As String)
    Dim x As Long
    Dim F As Double
    Dim T As Double
    Dim Start As Double
    Dim Stopp As Double
    Dim Min As Long
    Dim Day As Integer
    Dim OverMid As Boolean

    Select Case LCase(Weekday)
        Case "mandag"
            Day = 1
        Case "tirsdag"
            Day = 2
        Case "onsdag"
            Day = 3
        Case "torsdag"
            Day = 4
        Case "fredag"
            Day = 5
        Case "lordag"
            Day = 6
        Case "sondag"
            Day = 7
        Case "x"
            Day = 8
        Case Else
            Day = 0
    End Select

    OverMid = False

    If LCase(Holiday) = "x" Then Day = 8

    If Len(FromTime) = 0 Or Len(ToTime) = 0 Then
        Exit Function
    End If

    If Len(FromTime) <> 5 Then
        MsgBox ("Use format TT:MM - From time is wrong:" & FromTime)
        Exit Function
    End If

    If Len(ToTime) <> 5 Then
        MsgBox ("Use format TT:MM - To time is wrong:" & ToTime)
        Exit Function
    End If

    F = Val(Left(FromTime, 2)) * 60 + Val(Right(FromTime, 2))
    T = Val(Left(ToTime, 2)) * 60 + Val(Right(ToTime, 2))

    Start = Val(Left(StartTime, 2)) * 60 + Val(Right(StartTime, 2))
    Stopp = Val(Left(StopTime, 2)) * 60 + Val(Right(StopTime, 2))

    If T = 0 Then T = 24 * 60
    If T < F Then
        T = T + 24 * 60
        OverMid = True
    End If

    If Stopp = 0 Then Stopp = 24 * 60

    For x = F + 1 To T
        If x > Start And x <= Stopp Then
            Min = Min + 1
        End If
    Next x

    If OverMid = True Then
        For x = 0 To Val(Left(ToTime, 2)) * 60 + Val(Right(ToTime, 2))
            If x > Start And x <= Stopp Then
                Min = Min + 1
            End If
        Next x
    End If

    'If weekday is set, equal to day
    If Daynr <> 0 Then
        If Daynr <> 9 Then
            If Day <> Daynr Then Min = 0
        End If

        If Daynr = 9 And (Day > 5) Then
            Min = 0
        End If
    End If

    TimeValue = Min / 60

End Function

Private Sub Worksheet_Change(ByVal Target As Range)
 Dim streng As String
 Dim k As Long
 Dim r As Long

 k = Target.Column
 r = Target.Row


 If Cells(1, k) = "P" Then
  If Cells(r, k) = "x" Then
   Cells(r, 4) = "x"
   Else
   Cells(r, 4) = ""
  End If
 End If

End Sub