>I want to set the focus back to the previous active control
>when a button is pushed.
>
>How can I know which is the previous active control?

In your base textbox, editbox, etc. classes, add the following code to their
LostFocus events.

ThisForm.oLastCtl = This

In your button's Click event:

* Your code here
ThisForm.oLastCtl.SetFocus()

In your base form class, add oLastCtl as a custom property and add the
following to the Unload event:

ThisForm.oLastCtl = .NULL.

This was done on the fly, without testing, but it should get you pointed
in the right direction...