Locking data in specific row & column intersection

Hello Experts,

I am looking some help to find a way to lock specific interaction in a input form.

For example I have input schedule with Column A & B and Row 1 & 2 (as show below), I would like to lock (read only) A1 , B2 cells.

In my input schedule I have more intersections to be locked but I took small example below.

                                   A             B

                              1    L            input

                               2   input        L

1) I tried ready only with the intersection but it seems we can do only one intersection.

2) I tried formatting with Dimension Member/Property -> with specific member but seems it didnt worked.

     I selected row,Column as A/1 and locked the cell.

3) I cannot use UJ_VALIDATIONS in this case as the data for this intersection will be coming from Trial balance. I am trying to lock cells via this Input form.

Any inputs greatly helpful.

Thanks,
Srinivas Thota