matching different line number format in grep-mode

[Jim Newton]

I have an application which prints line number information not in the standard 
grep format but as follows.

at line 302 in file /full/path/to/file.ext

Is there something I can do to the variable compilation-error-regexp-alist-alist
which will cause grep-mode to also find these lines?  

I see the pattern when I look at the variable, but what's the flow to make 
either grep-mode or some other mode actually find these lines on next-error ?

Jim