Update Textbox From Modal Form

Hi everyone,

On my form I have button next to textbox to open modal form (bootstrap.widgets.TbActiveForm)

In this modal form user will have possibility to filter long list of values and chose only one.

To make it simpler lets say that on form (it don’t have to be modal form) there is simple dropbox.

My question is how can I update my textbox from first form with value from dropbox from modal form(bootstrap.widgets.TbModal) ?

Many thanx for any suggestions.