VBA form that disappears

Hi.

Sorry for my bad english.

I have an excel file with macros that uses a form who contains a listbox. Well... the forms disappears when the program starts. It take some time to populate it, and at the end of the routine, the form disappears. I have to launch another application (a browser or Explorer or whatever) and then close it, and finally clicking on my excel file, the form appears correctly.

I do this steps on my VBA code:

_ Set the form

_ form.show

_ in the "userform_activate" section, I populate the listbox from the cells of the current sheet (it takes some time... like half a minute)

That's it. At the end of the routine, the forms disappears.

How can I manage to avoid the disappearing?

Thank you.