Bibliography - GREP expression

Hi. (This may be a duplicate post, but it was lumped in to another post where it will get lost, so here we go again...  Please, Adobe, leave it as a separate query - it really is!!)
I need to be able to make just the first number within the parentheses bold, but not any others. In this sample, I have the solution:

(1) Surname Initial et al. Journal 2000;10:2XX–2XX; (2) Surname Initial et al. Journal 2000;10:2XX–2XX;
(3) Surname Initial et al. Journal 2000;10:2XX–2XX; (4) Surname Initial et al. Journal 2000;10:2XX–2XX;
(5) Surname Initial et al. Journal 2000;10:2XX–2XX; (6) Surname Initial et al. Journal 2000;10:2XX–2XX;
(7) Surname Initial et al. Journal 2000;10:2XX–2XX.

(?<=\()\d+.*?(?=\)) works well, but there are times when there is another number buried within each reference that can be in brackets, like this:

(1) Surname Initial et al. Journal 2000;10(23):2XX–2XX; (2) Surname Initial et al. Journal 2000;10(23):2XX–2XX;

What do I need to add to my GREP to only choose the first parenthethical number? I thought a second GREP would work, but, alas, no:

(?<=; )\d+

Any suggestions? They are all separated by a semicolon/space or semicolon/soft return, (which I guess may require yet another GREP! <sigh>) if that helps These are set scientific styles and unfortunately cannot be altered to make my life easier...