Okay, I see what you mean now.

If I changed the ControlTip text to an non-ambiguous format, like d-mmm-yyyy, and it works fine.

Other than that, I wouldn't use Controltip text, I would build it from the data on the form, like

[vba]

Private Sub D1_Click()
'Denne rutine, og alle de f?lgende, repr?senterer knapperne for dagene p? formularen,
'finder den nuv?rende v?rdi af teksten p? den knap der trykkes p? og placerer den i
'den aktive celle og lukker formularen
ActiveCell.Value = DateValue(D1.Caption & "-" & Me.CB_Mth & "-" & Me.CB_Yr)
Unload Me

End Sub
[/vba]