Sumproduct using data in different worksheets

[drluke]

[TABLE="class: grid, width: 250"]
<tbody>[TR]
[TD][/TD]
[TD]Yr
[/TD]
[TD]Per
[/TD]
[TD]Client
[/TD]
[TD]Amount
[/TD]
[/TR]
[TR]
[TD]East
[/TD]
[TD]2018
[/TD]
[TD]1
[/TD]
[TD]CXYZ001
[/TD]
[TD]1562.00
[/TD]
[/TR]
[TR]
[TD]East
[/TD]
[TD]2018
[/TD]
[TD]5
[/TD]
[TD]CBLG070
[/TD]
[TD]596.55
[/TD]
[/TR]
[TR]
[TD]East
[/TD]
[TD]2018
[/TD]
[TD]1
[/TD]
[TD]CXYZ001-10
[/TD]
[TD]8251.99
[/TD]
[/TR]
[TR]
[TD]East
[/TD]
[TD]2018
[/TD]
[TD]1
[/TD]
[TD]CBLG070
[/TD]
[TD]9426.33
[/TD]
[/TR]
[TR]
[TD]East
[/TD]
[TD]2018
[/TD]
[TD]5
[/TD]
[TD]CXYZ001-15
[/TD]
[TD]7491.76
[/TD]
[/TR]
</tbody>[/TABLE]


I have 4 worksheets with the same data per region. I need to sum sales by customer per period across all 4 worksheets into one single line in my summary sheet. In addition I need my formula to only look at the first 7 characters of the client code.

So, in summary I need a formula that will sum sales

If region = East go to worksheet 1 and sum sales if customer = CXYZ001 and period =1

Any suggestions?