I have a PCF that I've used for some time now, successfully. I need to modify it, in order to look at a count a few months back, so that I can recreate the stock list that met the parameters on that date. I'm struggling with it and could use some help please.

The PCF looks at the number of stocks up 25% in the last month. It reads as follows:

C20 >= 5 AND (AVGC20 * AVGV20) >= 2500 AND 100 * (C - C20) / C20 >= 25

As I say, it works just fine.

I need to look at the list of stocks that met this condition, on Dec 31, 2013 (which is 60 trading days ago as of March 28, 2014). I've tried every combination I can think of and cannot get it to come to the correct conclusion for that date.

Can someone help me?

Adding 60 to all of the bars ago parameters would result in:

C80 >= 5 AND (AVGC20.60 * AVGV20.60) >= 2500 AND 100 * (C60 - C80) / C80 >= 25

You could replace the bars ago parameters with dates as well. Assuming you want to use the last trading day of November 2013 as being a month before December 31, 2013:

C'11/29/2013' >= 5 AND (AVGC20.'12/31/2013' * AVGV20.'12/31/2013') >= 2500 AND 100 * (C'12/31/2013' - C'11/29/2013') / C'11/29/2013' >= 25

PCF Formula Descriptions
Handy PCF example formulas to help you learn the syntax of PCFs!