I have two userforms, form A and form B. Form A contains 10 textboxes
(txtbox1, txtbox2, ..., txtbox10), and form B contains a combobox and an OK
button.

What I want to achieve is as follow: whenever the user click one of the ten
textboxes if form A, form B will show. The user then select one value from
the combobox, click OK, and the selected value will be sent to the textbox
that was clicked initially. How do I make form B to recognize which textbox
that was clicked by the user?

P.S. Obviously, it will be easier if I can replace the ten textboxes in form
A with comboboxes, and eliminate the need to have form B altogether, but
unfortunately I do not have enough space in form A to do that. Each entry in
the combobox consist of 4 numbers followed by a description, and the
textboxes in form A have just enough width to show only the numbers.