Clearing text from a richtextbox from another process

Hello. I want to clean the contents from a richtextbox from another program(wordpad, for example), one which I do not control. I tried using EM_SETTEXTEX but it will only crash wordpad. I've read somewhere that you cannot use this message across processes. Is it true? If yes, which other methods could I follow to do what I need?

Thanks!

Hai PT
WM_SETTEXT WORKS
Try this...

Code:

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Sendmessage hwnd,WM_SETTEXT,0,vbnullstring

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