on the spreadsheet I have a rental complex with 50 units and I rent unit 1A I
would like that to reflect that the complex has only 49 available units left.
I understand how to subtract one cell from another but by using 1A that
formula doesn't work.
If cells A! to A50 contain the units and B1 to B50 indicate whether or not
they are occupied (blank meaning not occupied) then = COUNTBLANK(b1:b50) will
give number free.