VLOOKUP - Across Multiple Sheets

I'm having trouble with a VLOOKUP and need some help.
We have customers across various states and each state is further split up into various regions.
I have a sheet for each state, with its regions and its customers.

I want to create a VLOOKUP on the summary page, that will look at the respective state and return the result for that particular customer, region and month.

See attached for clarification.

Thanks!