According to what I have understood, what you need is from your application to intercept the resizing of other windows in the system to adapt them to what you need.
A priori I would advise against this, because it can have some disadvantages.
There is no way to capture that "event" at the level of all applications from yours easily; I can think of a system hook , but it's not trivial.
On the other hand you do not know what applications are running on the system and their behavior (and how they have been programmed). Changing the properties of the window from yours can cause errors or failures in the display according to your changes.
Depending on what you are saying, you should not only change the size but also the state . If a window is axed, you will have to change that state, restore it and modify the size, which can also give you problems (following the same logic of the previous point).
I said, a priori the solution you propose does not seem the best.
Maybe you should review information on how to create a DeskBand or how to convert yours to one. In that case, these problems of size of other applications would have solved them.