... request, whether a textbox contains a certain letter ?

How do I request, whether a textbox contains a certain letter ?

For example , when the letter "p" is entered into a TextBox i want something to happen...

Or... how can I make that Keyboard Events are still executed, while there is something written in an active TextBox ?

You can either check as the person is typing or afterwards using the find system text expression.

find(src, text)

It will return a -1 is the letter is not there.

Thanks a lot !