How to send click event to invisible window's buttons?

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PowerBuilder

I have a scenario where some windows are required to be automated non-visually from a controller window, that opens, sets parameters and send events to the other windows controls, like SetFocus (mostly text boxes) and Clicked (exclusively to buttons).

The process works fine when the controlled windows are visible, but it doesn't work when they are invisible.

It's a MDI application.

Some ideas on how to do that?

Thanks in advance.

What I have tried:

I tried to set the Width and Height of controlled windows to 0, but the title bar still shows up. The controller window can't be application modal (Response kind).