Print to File - Append to File?

I have set up a Print to File - Generic/Text Only printer. This is working
fine. But the program I am printing from seems to be sending every line of
print separately, that is, when printing, the window pops up and asks for a
file name for every line of print, and then saves each line of print in a
separate file. I could have 1000 lines of print, and would have to enter 1000
different file names for each file.

I am sure the actual problem is from the program I am printing out of,
because if I print a test page, or out of Word, I don't have this problem.

Is there some way to configure the print to file to append all the text to a
single file as it receives text?

I might be able to add printer codes to the end of the lines being sent from
the program I am printing from. Is there a control code I could add that
would tell the Generic/Text Only driver not to start a new file?

Or any other methods of getting all these lines of text into a single file
without having to manually enter thousands of file names first?

Any suggestions would be appreciated.