keeping focus in a field

[viktoras d.]

there is a field and a menu button on my stack. If I write some text in 
the field and select portion of it, then go to menu and choose whatever 
I wish from the pull down list, it keeps focus on the selection of text 
in the field.

But if I create a context menu using popup button, the selected text in 
field looses focus at the moment the popup is called. Is there any 
simple trick (I already know complex ones :-)) to force the selection to 
persist, so I could handle it from the context menu ?

Viktoras