How do I delete first letter of a text?

Hi...I amd a teacher and trying to make a spelling game. It is a kind of fast writing a word you see.

I can delete the first letter by pressing any key in the keyboard with this code..

right(SpriteFont.Text,len(SpriteFont.Text)-1)

but I want to delete the first letter with a specific key "A, or B" I press

For example: the word is " book"

I want it delete the first letter only pressed on the key "B"

Thank for your help...

try:

http://lookpic.com/O/i2/1384/eJkaBhU2.png

http://lookpic.com/O/i2/1756/Lqrh4meb.png

Thanks

Well this sucks...

Well this sucks...

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