Regular expression question -- exclude substring

[dreamerbin at gmail.com]

Hi,

I'm having trouble extracting substrings using regular expression. Here
is my problem:

Want to find the substring that is immediately before a given
substring. For example: from
"00 noise1 01 noise2 00 target 01 target_mark",
want to get
"00 target 01"
which is before
"target_mark".
My regular expression
"(00.*?01) target_mark"
will extract
"00 noise1 01 noise2 00 target 01".

I'm thinking that the solution to my problem might be to use a regular
expression to exclude the substring "target_mark", which will replace
the part of ".*" above. However, I don't know how to exclude a
substring. Can anyone help on this? Or maybe give another solution to
my problem? Thanks very much.