Q: Change column references by dragging down rows I have this equation in excel =COUNTIF(A2:A10001,"<0.5")
Is it possible to make it so that when this formula is copied down the formula becomes =COUNTIF(B2:B10001,"<0.5") and so on?

A: Here's a way to do it by modifying your formula a little.  It uses the OFFSET function to pick the column based on the row.
=COUNTIF(OFFSET(A$2,0,ROW()-1,10000,1),"<0.5")

This anchors the reference to A2, and the range is defined as offsets from there.  There is zero offset for the starting row. The column is offset based on the row number.  In my test, I started the results in row 1.  The first result you want is for column A, which is zero column offset from the reference point, so I subtract 1 from the row number.  You would need to change the adjustment if you start in a different row.  
The last two OFFSET parameters return a range with a height of 10,000 and a width of 1.  COUNTIF then works on that range.  When you drag or copy this down, the row number drives the column selection.
