A simple regexp question

Hello all,

I have a conceptually simple problem... I have a text file that i've read in as one long string. At various places in this string is the pattern cx="<a number>". The numbers are integers but may contain any number of digits. I'm trying to extract all such numbers from the string. Can this be done easily with regexp? I suspect it has a very simple solution, but i can never quite figure out regexp.

Thanks,
Matt