I would like to replace the 'a1' with a String variable I have defined
earlier in the script in the following line:

ActiveCell.FormulaR1C1"=SUMIF('1a'!R6C1:R[32]C1,R5C1:R[32]C1,'1a'!R6C10:R[32]C10)"

I am trying to automate the creation of summary lines on a sheet for a
range of sheets in my workbook.