Create a script in Customer Database like this:
Go to Layout "Customer Data Base" (Customer Data Base ) ]
Enter Find Mode 
Set FIeld [Customer Data Base::Customer Number ; Get ( ScriptParameter ) ]
Pause/Resume Script [indefinitely]
Let's say you name that script "Find Records".
Then modify your original script to be:
Perform Script ["Find Records" from file: Customer Data base ; Parameter: Annual::Customer Number ]
I am assuming that the file has the same name as your table. If not the text in blue will need to be changed to that of the file name. These scripts also leave any data previously copied to the clipboard intact--which will make your users happier with your database when data they may have copied doesn't disappear every time they run your find script.
So, what you are saying is that I need to run a script that is in the Customer Data Base? And run that script from the initiating file? Hmm. Hadn't thought about that. Seems counter-intuitive.
Thanks a million.
Scripts can only interact with windows from the same file as the script. But once upon a time, each FileMaker table had to be defined in a separate file. So FileMaker has long supported the ability to perform a script in File A from a Script in File B. The ability to pass data in a script parameter is a newer option that makes this work even more nicely than in the "old days" when we had to park data in a global field and use a relationship to retrieve it when the script in the second file began execution. (Yes, you could copy it to the clipboard like you've done here, but that wasn't the best way to do this back then either...)
As I was creating the script, deja vu happened. 35 years ago I wrote FORTRAN code. I passed parameters in subroutines the same way. That's awesome.
Thanks for your help
Of course, in Fortran, you can define a whole set of parameters. FileMaker supports just one, but there are several ways you can use to combine values so that you can still send multiple parameter values to the Subscript.