How to paste text to other window's active textbox

Hi all,

I am doing a clipboard manager and i need to add a function to direct paste text to other window's active textbox.

By this: I make the form on top and when i double click on the listview item (i show the items in a listview) i need it to paste the text in it to the selected textbox in the other window.

 

Can anyone help me please.

 

Thanks