Userform - Auto-populate text box

Hi There,

I think what I'm trying to achieve is pretty simple, but I've had no luck so far.

Basically I have two text boxes. textbox1 allows the user to input a date, textbox2 is supposed to auto-populate a date which adds 6 weeks (42 days) to the date in textbox1. I tried the below code but had no such luck .

Thanks for any help in advance!

Private Sub textbox1_Change()
If textbox1.Value = "" Then Exit Sub
textbox2.Value = CDbl(textbox1.Value + 42)
End Sub