If you were using FileMaker 11, you could do this with a portal filter and a summary field defined in Table B, but since you do not, you'd need to set up 12 different relationships for each of your 12 different portals. I'll walk you through setting up the first such portal and you can just repeat the process to create the other 11.
I'm going to use "A" as the first Parent Code.
In Table A, define a calculation field, cAKey, as returning type text and enter "A" with the quotes as its calculation.
In your relationships graph, click the Box for Table B to select it, then click the button with two plus signs to make a new table occurrence box that also refers to the Table B data source table. You can double-click this box and change its name to "ParentCodeA" or some such descriptive name.
Drag from Table A to ParentCodeA so that initially, it has the same relationship that you've already set up for your first portal. Then drag from Table A::cAkey to ParentCodeA::Parent Code so that the relationship is now:
Table A::YourPrimaryKey = ParentCodeA::YourForeignKey AND
Table A::cAKey = ParentCodeA::Parent Code
Now you can create a portal on your tab to ParentCodeA to see a list of just the Parent Code A related records.
If you define a calculation field in Table A as: Sum ( ParentCodeA::Divided Minutes ) you'll get a calculation totaling Divided Minutes for all the Parent Code A records in your portal.
Repeat this process for each of your remaining 11 parent codes and you'll get what you requested.
I think it is all clear to me. I will study it further then try to implement the solution. I'll get back with you if I have difficulty.
By the way - can FM Pro 11 Advanced be run off of a FM Pro 9 Server?
Yes. The file formats are the same. Any features specific to 11 that are executed on the server side, will not function. You might try downloading the trial and testing with it to see how it works for you.