Excel Cell reference that will go to the left

I am using an excel spreadsheet formula to add two cells together and I want to have it reference one row from left to right like it normally does, but I need it to reference the same row in another page in reverse, and then be able to drag the formula through the entire worksheet. I cannot seem to find anything like this when I look online. TLDR I need to know how to tell excel reference the cell to the left if I drag it to the right.

so I need to add A0 in page one and A9 in page two then when I copy the formula to the left I need it to grab A1 and A8, is there a way to get this?