Userform Date Format Issues

Hi,

I have created a user form for users to input data onto a spreadsheet. All works find but I wanted to put some error validation into it to pick up input errors. The issue I have is I can't get the CDATE function to understand an incorrect date. If the user inputs the date as 01/02/03 it will happily put 1st February 2003 - Perfect!! But if I put in 32/02/03 to generate an error the system happily puts the date as 3rd January 1932.

Please see my code here.

    Dim DateOfJoining As Date
    Dim MaternityStartDate As Date
    Dim ExpectedWeekConfinement As Date
    Dim QualifyingWeek As Date
    Dim ForthWeek As Date
    Dim MonthOne As String
    
    Dim MonthTwo As Double
    Dim PayDay1 As Date
    Dim PayDay2 As Date
    
    Private Sub CalculateButton_Click()
'Make Sheet Activate
    Sheet1.Activate

    

'Insert Details
Start:
    
    MonthOne = TextBoxDay.Value + "/" + TextBoxMonth.Value + "/" + TextBoxYear.Value
    DateOfJoining = CDate(MonthOne)
    On Error GoTo DoJerror
    MaternityStartDate = TextBoxmsDay.Value + "/" + TextBoxmsMonth.Value + "/" + TextBoxmsYear.Value
    On Error GoTo MSerror
    ExpectedWeekConfinement = TextBoxewcDay.Value + "/" + TextBoxewcMonth.Value + "/" + TextBoxewcYear.Value
    On Error GoTo EwCerror
    QualifyingWeek = ExpectedWeekConfinement - 104 - Weekday(ExpectedWeekConfinement, vbSunday)
    
 If (Weekday(ExpectedWeekConfinement, vbSunday) <> 1) _
    Then ForthWeek = ExpectedWeekConfinement - Weekday(ExpectedWeekConfinement, vbSunday) - 27 _
    Else ForthWeek = ExpectedWeekConfinement - 28
 

    Range("F6").Value = MonthOne
    Range("C2").Value = TextBoxName.Value
    Range("C3").Value = TextBoxNumber.Value
    Range("C5").Value = DateOfJoining
    Range("C6").Value = MaternityStartDate
    Range("C7").Value = ExpectedWeekConfinement
    Range("C8").Value = QualifyingWeek
    Range("C9").Value = ForthWeek
    
    Range("B15").Value = Format(PayDay1, "mmmm yyyy")
    Range("B16").Value = Format(PayDay2, "mmmm yyyy")
    
    Range("C15").Value = CCur(TextBoxMonth1)
    Range("C16").Value = CCur(TextBoxMonth2)
    
    Unload Me

GoTo EndSub


EwCerror:
     MsgBox "Please enter a valid date for " + Label12.Caption
          GoTo Start
DoJerror:
     MsgBox "Please enter a valid date for " + Label4.Caption
          GoTo Start
MSerror:
     MsgBox "Please enter a valid date for " + Label8.Caption
          GoTo Start




EndSub:

End Sub




Private Sub CheckBox1_Click()

Start:
   
    On Error GoTo DoJerror
    DateOfJoining = Day(TextBoxDay.Value) + Month(TextBoxMonth.Value) + Year(TextBoxYear.Value)
    On Error GoTo MSerror
    MaternityStartDate = TextBoxmsDay.Value + "/" + TextBoxmsMonth.Value + "/" + TextBoxmsYear.Value
    On Error GoTo EwCerror
    ExpectedWeekConfinement = TextBoxewcDay.Value + "/" + TextBoxewcMonth.Value + "/" + TextBoxewcYear.Value
    
    QualifyingWeek = ExpectedWeekConfinement - 104 - Weekday(ExpectedWeekConfinement, vbSunday)
    If (WorksheetFunction.EoMonth(QualifyingWeek, 0) >= QualifyingWeek) _
        And (WorksheetFunction.EoMonth(QualifyingWeek, 0) <= QualifyingWeek + 6) _
            Then PayDay1 = WorksheetFunction.EoMonth(QualifyingWeek, -1) Else PayDay1 = WorksheetFunction.EoMonth(QualifyingWeek, -2)
    PayDay2 = WorksheetFunction.EoMonth(PayDay1, 1)
    
    If CheckBox1.Value = False Then
    PaymentInst.Visible = False
    Month1.Visible = False
    Month1.Caption = Format(PayDay1, "Mmmm yyyy")
    TextBoxMonth1.Visible = False
    Month2.Visible = False
    Month2.Caption = Format(PayDay2, "Mmmm yyyy")
    TextBoxMonth2.Visible = False
    
    Else
        
    PaymentInst.Visible = True
    Month1.Visible = True
    Month1.Caption = Format(PayDay1, "Mmmm yyyy")
    TextBoxMonth1.Visible = True
    Month2.Visible = True
    Month2.Caption = Format(PayDay2, "Mmmm yyyy")
    TextBoxMonth2.Visible = True
    End If
    
GoTo EndSub


EwCerror:
     MsgBox "Please enter a valid date for " + Label12.Caption
     CheckBox1.Value = False
     GoTo Start
DoJerror:
     MsgBox "Please enter a valid date for " + Label4.Caption
     CheckBox1.Value = False
     GoTo Start
MSerror:
     MsgBox "Please enter a valid date for " + Label8.Caption
     CheckBox1.Value = False
     GoTo Start
EndSub:
    
End Sub

Private Sub CommandButtonClose_Click()
Unload Me

End Sub

Can anyone let me know where I am going wrong! Or see a better way to achieve this.
I do not have DatePicker as an additional option in my Userform tool box and do not have admin rights on this machine to install it.

Thank you in advance.