if you have a Unix box (or egrep on
a DOS machine, but syntax may be
different):

copy the text-to-be-cmtd to a file
add ";tmp " comments with:
sed -e 's/^/;tmp /' file > file2
copy file2 back onto the
text-to-be-cmtd in the original
source file.

i saw a set of Unix-like tools for DOS,
once. it might be around on the net.

james