Here is my problem,

I am trying to return a cell value using a cell name as a result of the
concatenation of two fields.

Example:

Sheet A has a cell named P1_1 which contains a value.
In Sheet B I am concatenating cell A1 (P1) with cell B1 (1) as follows:
=concatenate("+",A1,"_",B1).
Excel inserts "+P1_1" into the cell where I inserted the formula i.e.
Excel inserts a string of text. I would like the value of the cell
named P1_1 to be inserted instead.

Any clues out there on how to achieve this?