I am trying to minimize the amount of space this spreadsheet takes up. I
have Three colums. The first column is the category type (39 or 41). The
second column is the estimated cost before construction. The third column is
the actual cost. What I want to do is average the difference between
estimated and acutal cost for each category. There is no pattern to the
category selection. It depends on the job. I was trying to write an if,
then, statement but it has been awhile and I am not sure if you can do it
anyway. It was something like this...

average(IF(column1=39,(column2-column3)/column2),else if(column1=41,skip to
next row))

If you can make sense of all this let me know.