Not quite sure what you mean here:

.... One question I have is can I use these forumulas on a separate sheet within the same workbook? ......

Isn't that exactly what the example does?
Do you mean if the formulas can be used on more sheets within the same workbook?

One more question by the way - will your table always contain only "1" or blank?

Yes the table would always include either "1" to identify the intersecting row of the tractor and the parts available or it would be left blank.

The other question was in reference to the formula's working on one sheet but the actual tractors and parts on a different sheet or tab. I would like there to be two and maybe three tabs (or worksheets) in the file. The shop mechanics would use sheet 1(possibly labeled parts lookup, and would only see the popup box and the parts available. Sheet two would be used by the shop foreman and would be the actual table with all the tractors and parts. This table will end up very large as we have close to 100 pieces of equipment and hundreds of parts.

Matt