It should read A1 and write at A2. Read at B2 and write at B3. read at C3 and write at B4.

The number part of the cell address seems obvious. Just do a normal counter that increases by 1 with each loop.

But what about the LETTER part of the cell address? How to I increase it along the alphabetical order (and beyond, like AA, AB, AC, etc)??

Does UIpath reads integer variables as a letters (1 = A, 2 = B, 3 = C, etc, etc)?

IF it does, how do I insert both variables (the one for row and the one for column) in the Excel Read and Excel Write activities? (let’s call the two integer variables as RowVar and ColVar)?

In the field of the Excel Read and Write Activities where I tell the cell, would I just add ColVar RowVar, or ColVar+RowVar…???

Please check Conversion from integer to Excel Column (Base 26) A-Z/AA/AAA etc - #11 by jessbrian for the conversion of numbers(coresponding to the column number) to letters (coresponding to the column names used in excel).
And for the read and write activities, if ColVar contains a letter, and RowVar contains a number, you can use them in that field like ColVar+RowVal (carefull at spaces).

UiPath should have a ready solution for the Excel activities where you could just give the activity two integer variables for column and row and it would automatically interpret the column one as letters.