Hello. I added this code to about 200 cells in a tab. =IFERROR(HLOOKUP($B16,INDIRECT("'"&TEXT(EOMONTH("12/31/2012",COLUMN(F16)+ROW(F16)-7),"mmmm yyyy")&"'!"&"$C$2:$O$35"),34,FALSE),0)

Now, my workbook is running very slow. When I ran a macro that worked perfectly before, it froze up. I think that has to do with these formulas. The formulas look for different tabs in the workbook and then do an hlookup. Is there a more effecient way of writing this formula?