Macro to insert formula using Autofilter
 

I'm trying to create a macro that will select a range of rows fitting
a certain criterion, then insert today's date into an empty cell in
each row that matches the criterion. I set up the macro to insert the
formula into the top cell of the range and then copy the formula down
the range. My problem is that I have to run this macro daily, and the
range of rows changes every day. I set up the macro using today's
report, so it contains today's ranges, but I need to alter the macro
so that it selects the active range for each day. Here is the relevant
portion of the macro:

Selection.AutoFilter Field:=8, Criteria1:="Ad"
Range("L87").Select
ActiveCell.FormulaR1C1 = "=TODAY()"
Selection.Copy
Range("L307:L5100").Select
ActiveSheet.Paste

I'm a complete novice at macros, so if anyone has any ideas for a code
that would work, please help!

Thanks,
Jill