Dynamically-updated-ticker-list

I would like to be able to use specific tickers for a particular date. As an example consider the csv file snippet below:

2012-03-16,PATK,REX,CKEC
2012-03-23,PATK,CKEC,REX
2012-03-30,PATK,CKEC,AACC
2012-04-06,PATK,AACC,BXG
2012-04-13,BXG,CKEC,LUB
2012-04-20,BXG,PTGI,CHDN
2012-04-27,PATK,BXG,PTGI
2012-05-04,PATK,BXG,KTCC
2012-05-11,JBSS,PATK,BXG
2012-05-18,JBSS,ADGF,BXG
2012-05-25,RDI,PATK,BXG
2012-06-01,SYPR,RDI,GTSI
2012-06-08,SYPR,RDI,PATK
2012-06-15,INMD,SYPR,RDI
2012-06-22,BBGI,NATH,UTMD

I could format the file to json, if that helps.

How can I go about having a changing basket of stocks, given a particular date?

Thanks much,
Evan