VLOOKUP Find values from multiple worksheets

[Strugggler]

I believe this could possibly be performed using a VLOOKUP formula, but I'm not sure.
I want to find sum of all 4 returned values (Sales!BL5, Sales!BM5, Grants!X5, Deferred Pymts!X5

Column References:

Cell AD2 (AMOUNT TOTAL PYMTS)
Cell AC2 (TOTAL NO. OF ORDERS)
Cell Range B5:B4833 on multiple pages (CUSTOMER NAME)
Cell Range AJ5:AJ4833 on multiple pages (CUSTOMER NAME)

Formula:

In Cell AD2 of CustomerData! Sheet:

If AC2 is not blank, then
look for match between A2 and Sales!B5:B4833, return the value in Sales!BL5, and
look for match between A2 and Sales!AJ5:AJ4833, return the value in Sales!BM5, and
look for match between A2 and Grants!B5:B4833, return the value Grants!X5, and
look for match between A2 and Deferred Pymts!B5:B4833, return the value Deferred Pymts!X5

Hope this does not confuse, but if John Doe is listed in AC2 I want to find the sum of his total payments if his name is listed as a customer in Sheets Sales, Grants, and Deferred Pymts. The Sales! sheet is divided into AM and PM pricing which explains why Sales! has Column B and Column AJ for Customer Names.