COUNTIF based on Data Validation dropdown choice

Ok. I have a table of values. In Column A1-A368 I have 27 regional office names (chicago, LA, so on and so forth) appearing multiple times. In columns B-AA (and from rows 1-389) I have values of A, B, C, or D so that each regional office name in column A has values in each row from B-AA. I want to look through Column A and find all the names of one regional office (I.E. chicago) and find out how many times the value of just one value (in this case A) is in Column B for JUST THAT OFFICE and that answer will go in cell B 369. Then I would have a separate formula to do the same in column B. So on and so forth.

Now...the tricky part is.....what I want to do is in Cell A 369 have a validation list so whatever value I choose from the List (say I choose Chicago), the formula in cell B389 will adjust and only count for the value in A389

is this possible?