Hi Geoff

If I want to interact with other applications or other
workbooks when my data input form is used, I know I must
make the form modeless, but how do I install Minimize and
Maximise buttons in the form title bar?

Talking of the FormFun sample , it raises some interesting effects/errors when it comes to
states of "modeless". I have no solution to this yet, but it is interesting to look into.

If you have VB6 to play with, a vb addin with a "real" vb form is better suited for
cross-app Windows than an Office Userform

Must I prefix
all my Sheets references to be safe

Yes. You can assume nothing and expect the worst from any user, yourself included. Time
spent on safe code is better use of time than cleaning up disasters caused by intelligent
systems and not-so users ;-)

HTH. Best wishes Harald
Followup to newsgroup only please.