Programming question for unix regular expression guru

[mrscintilla]

I need some regular expression programming help.
basically I want to be able to search all instances of word X occuring within 100 characters of word Y in a bunch of files.

How do I form a regular expression that can do that? I'm using grep in linux.

Thx,

 

[notfred]

wordx.{0,100}wordy|wordy.{0,100}wordx