Review your '@lookup' function under the database section of help. You'll find usefull things that will allow you to pull it out of other workbooks, maybe being worked on by someone else. The most simplist procedure is to create your formula so that where it requires the results of the cell on page one, literally goto page one and touch the cell. Excel will automatically create the reference info for you. If you don't need to process the results of the previous page, just show it, same thing, touch the reference cell and it will appear and change as the other cell does.

I wrote a program to do contract work for customers, where page one was the totals for each section of work to be completed. On page two, were the adds created by the owner for additional fees and they were added to the base bid. Progress payments were made based upon agreed amounts of work that would be done before we could get a draw against the total. SO, in layman english, you would have Contracted Amount + Additional Work to be Performed - Progress Payments = Remaining Total Due. The command would look like this =PROPOSAL!L13+'ADDS - PMTS'!L15, where "Proposal" is page 1, the '!' tells Excel that it a sheet name, then the row & column numbers on that page. In this case, page 2, 'Adds-Pmts' sheet has already processed some information and is requiring the info off of page one, to make it's final summation. In the example above, the single quotes represent the active page making the call for the information.