BTW I'd be remiss if I didn't mention how 'dangerous' it is to use textboxes that way. I don't know where the dates come from but when they are in a textbox the user can change them or just enter something that doesn't translate to a date so you should at least do something like this:
Code:
If Not IsDate(Text1.Text) Then
MsgBox "The text in Text1 is not a valid date"
Exit Sub
End If
If Not IsDate(Text2.Text) Then
MsgBox "The text in Text2 is not a valid date"
Exit Sub
End If
MsgBox Abs(DateDiff("h", Text2.Text, Text1.Text))
If the dates come from some source other than user input then you should probably use Labels instead of textboxes and in the formula use Label1.Caption instead of Text1.Text etc.