Show a childform without losing focus on parentform

Hello,

I need some help on a problem.

How can I show a childform, but without losing the focus on the parentform?

I have a button on a form. When you click the button, another form should
appear just below the button. On the popup form, are other controls. When you
put the focus in one of these controls I don't want to loose the focus on the
parent-form (look at the caption-bar).

In fact you could see it as a combobox. When you click the dropdownbutton,
the list-form appears (in my case it would be a user created form). Only
difference is offcourse, that the dropdown form can be outside the
parentforms bound (which can't happen with a combobox dropdown).

Any ideas how to make this possible?

Best regards,
Ike