>I created a class based on a text box. I let the user to change the value of a text box pressing CTRL+P (Return "Positive") And pressing CTRL+N return "Negative".
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>I do this using keypress event. The problems is the CTRL+N return a strange character before "Negative", something like "|Negative". This strange character is CHR(14), I need to solve this as soon a possible.

I see nobody answered this, did you ever solve the problem?

What about an alternate interface that uses a combobox instead. In your case the user tabs or clicks to the textbox, then presses ctrl-n. With a combo then could just press "n". Saves a keystroke. Or you cold use radio buttons or in the valid of the text box replace "n" with "negative". Just some ideas.