Can't get a macro to run if a criteria is met.

[owen4512]

Here's the Vb Code I used but I keep getting a "Argument Not Optional" message box.

I want for the macro to run if the value equals to "Iawn I Bwcio". But if the value equals to "Dyddiad Anghywir"
then I want a message box to appear and say ;
"Mae yna dyddiad anghywir wedi ei fewnbynnu! Mae angen newid hyn er mwyn cario ymlaen!"

Private Sub mewbynnuDataSioe(ByVal target As Range)
    If (Range(D5) = "Iawn I Bwcio") Then
    '
    ' Mewnbynnu_Data_Sioe Macro
    '
    ' Keyboard Shortcut: Ctrl+Shift+Q
    '
    Range("E3").Select
    ActiveCell.FormulaR1C1 = "1"
    Range("E4").Select
        ElseIf (Range(D5) = "Dyddiad Anghywir") Then
        MsgBox "Mae yna dyddiad anghywir wedi ei fewnbynnu! Mae angen newid hyn er mwyn cario ymlaen!"
        
    End With
    End If
    Exit Sub
End Sub

Thanks in advanced, Owen.

 

[owen4512]

Thanks everyone for the help!

Thank you RoryA, that code worked