Help with stripping value from return string

[eluser]ppwalks[/eluser]
Hi all, got a bit of a problem and wondering if anyone knew of a way to tackle this problem, I have a search field to search specific data compiled of {letters - numbers - letters}, what i need to do is trim of the letters after the numbers, each record has a different string length which is why i cant just remove after a certain amount of characters.

Anyone ever done anything like this before or could point me in the right direction,

thanks all

Paul