font-lock and multiline comments

[bmaron2@hotmail.com]

I am writing a new major mode for an in-house programming language.
We'd like to have emacs do syntactic highlighting on the comments. The
language supports two kinds of comments:

// In-line C++ style comments

Comments
  Multi-line comments flagged by Comments/EndComments
  Here is another line
EndComments

The in-line style I was able to easily add with a syntax table
modification. The multi-line comments, however, I can't do because the
syntax tables only support comment syntax with 1 or 2 characters.

I then turned to font-lock mode. Adding the following font-lock
keyword didn't work if there were more than maybe 7 or 8 lines between
Comments and EndComments:

'("^[ \t]*Comments\\(.\\|\n\\)*EndComments" . font-lock-comment-face)

Apparently font-lock regions aren't designed to span multiple lines?

Can someone tell me how to get font-lock to recognize and properly
mark these multi-line comments?

Many thanks!!