PopUp/DropDown Menu referencing a cell with a formula?

Firstly, I know the extreme bare-bones of data sheets like Numbers. I am creating a monthly budget. (I do not like the too basic budget template offered in Numbers). Based on the Budget Template offered, how do I, if it's possible, have the PopUp/ DropDown Menu reference a range/row in another sheet? The example would be:

Charitable Donations as the DropDown option. Click on it. BUT, in the secondary sheet, I have recorded each month's donations in a row. So I have 12 entries. I want to be able to choose any one of those month's Charitable Donations to compare on the first page of my Workbook where the DropDown menu is located.

Please guide me through accomplishing this one way or another as "simply" as can be done.

This whole workbook is actually an expense workbook for self employment. So I have a yearly table on each sheet for the various expenses. I roughly have 20 sheets from Charitable Donations, Job Materials, Job Labor, Office, Tolls, etc., etc. Some of the sheets have additional tables with those expenses broken down further for other needed references come tax time. I also have an OverView table of all expense worksheets listed on this page. So keeping it separate is good for now, unless someone can reduce the work/entry being done. 🙂 So here, as you can see, monthly breakdowns. How do I have a DropDown Menu reference any Expense to any respective month to compare to a set monthly budgeted amount? Here is the offered Template. I like the idea of it. But I want a DropDown in Actual Column to reference an Expense in any Month chosen.

Does this make sense? Thanks for your thoughtful insights whether telling me its a terrible idea or help me to simplify it! 🙂 Lb