one book, to print on 2 presses

[triple one]

I'm printing a 100 page book. some pages are in color, some are in black and white.
i work in a small commercial print shop, and to keep our costs down we are printing the black and white pages on one press, and the color pages on the 4 color press.
in the past ive created 2 documents, since anything going to the 4 color press has to have specific paper sizes, crop marks and color bars, where indesigns default printers marks dont work.
the black and white pages can stay on their 8.5 x 11 spreads sending to a tabloid size plate, where the color pages have to be on a 12.5 x 19 size document in order to come out in the right place on the plate.

is there ANY WAY i can keep this in one document with 2 document sizes, and save myself a lot of time and hassle?

[DCurry]

Can you print to a larger media size? Set up a slug area to put your color bars and marks in. When you print the 1-color stuff, don't include the slug and print to 11x17 media size. When you print the color pages, include the slug and print to 12.5 x 19 media size.

[triple one]

THATS EXACTLY WHAT I NEEDED TO KNOW.
my boss is proud of me for how much time i just saved. I told him sometimes we just need a little help from our friends.
Thanks so much!

funny, he's 76 years old, owned this shop for over 30 years, and didnt know what slug area was.

[DCurry]

Awesome - glad it worked for you!