escaping special characters does not seem to be escaping in query

[ramdev.wudali]

Hi All:
    I have a few fields that are of the form: "A:2B" or "G:U2" and so on.  I 
would like to be able to search the field using a wild character search like:   
A:2*
or G:U*. I have tried out modifying the field_type definitions to allow for 
such queries but without any luck

Could someone/anyone provided me with a fieldtype that uses the canned 
Tokenizers and filters which will allow me to do a search as described ?

Thanks much

Ramdev