File splitting based on predefined hex and/or text string

[Qyot27]

Couldn't think of a more concise title.

I'm trying to get the images out of the .PCK files from the Mai-HiME PC game (link to game's amazon.co.jp page), and I've figured out that they are merely nothing more than concatenated .CRX files - .CRX being the graphics format other images in the game use; the only converter I know of that works with the game only supports .CRX. With the .CRX files that I pulled out of the .PCK archive by going in with HxD, selecting everything between occurrences of the text string CRXG, copy-pasting-and-saving to a new file with .CRX extension, and running the converter as usual on the new files, everything worked fine.

However, what I'm looking for is a less tedious way of going about this - I don't want to have to manually copy-and-paste all these files myself (especially because the .PCKs hold more than one image, and there's 102 .PCK files), so I want to know if there's some hex editing program out there or some method which will neatly divide up the .PCK files just prior to each time CRXG occurs in the text area. The massive null space between the files doesn't affect the converter's ability to deal with the images either, if that matters - just so long as CRXG is the very first set of characters, it's happy.