Dynamic list of customers

Sheet1 named "Alignment" (contains alignment of our sales people):
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Column A= Customer List of ID's
Column B= Salesperson 1 ("yes" in cells below if he has that customer)
Column C= Salesperson 2 ("yes" in cells below if he has that customer)
Column D= Salesperson 3 ("yes" in cells below if he has that customer)

Sheet2 named "Customer Listing":
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Cell A1= drop-down selectable list of our sales people
When a salesperson is selected I need a list of all their customers to appear on the sheet.

I would prefer to do this with formulas rather than code. I remember reading somewhere a while back that with dynamic ranges and maybe the Offset(?) function this could be done formulaically. Is that possible?