I'm with Craig on wishing to see a little more information before offering advice but here's some generic thinking.
IF, by any chance and perhaps unusually, your DETAIL records can be made to include the Branch Code every time they appear then you could consider using the Branch Code as the trap or part of it.
In that way the only detail records you would extract would be for the branch you wanted to report about.
More likely is that the branch code appears in a Page Header, Append area or, rarely but possibly, just a footer.
In that situation you need t trap and map your details records, add the branch code as a field from the Page Header, Append or Footer, fill the table (assuming you are using Monarch Classic, and then set up a FILTER to include only the Branch you wish to select for output activity.
This would be the normal approach since most reports in multi-branch business operations will report the same or similar information for every branch and filtering is a great was of getting separate outputs for every Branch from a single extraction process.
If neither of those option work for you I look forward to seeing the nature of your problem in some sort of example if you can provide one.
Please relay on this sample, because I cannot show the original data.
For example, this is the pdf file that I'm working on.
Branch 1 Cat 1 Cat 2 Cat 3 Cat 4 Cat 5 Measure 1 0 0 0 0 0 Measure 2 0 0 0 0 0 Measure 3 0 0 0 0 0 Measure 4 0 0 0 0 0 Measure 5 0 0 0 0 0 Branch 2 Cat 1 Cat 2 Cat 3 Cat 4 Cat 5 Measure 1 0 0 0 0 0 Measure 2 0 0 0 0 0 Measure 3 0 0 0 0 0 Measure 4 0 0 0 0 0 Measure 5 0 0 0 0 0
All I want to get is the "Branch 2", plus how will I can make the header "Measures" getting the "Cat" as their type.
All of the above suggestions will work, I just thought I'd throw in another option so you have more to choose from. I'm not sure what version of Monarch you are using, but in the more recent versions, additional template types are available such as Start Region and End Region. If your goal was to just import Branch 2, you can set the Start Region using "Branch 2" and you can set the End Region to when it detects "Branch 3".
Reach out if you have any questions.