Text file update

I have a text file that is a script for sybase 7. In the text file are dates that need to be updated before running a batch file that loads the files into dbisql. Currently I am having to manually update the correct dates before launching the batch files. Not to difficult but I have many date fields and many text files that have to be updated, which takes about 20 minutes. Any way to write data to a text file where there are dates.

Field data looks like this:
and year(transdate) = 2006
and transdate <= '2006-09-30' Thanks.