How?: Dropdown menu selection dynamically alters selects of other dropdown menus on same page?

How?: Dropdown menu selection dynamically alters selects of other dropdown menus on same page?

Hi
 
I have a project where I need a selection of one dropdown menu may affect the select of multiple other dropdown menus on the same page.
 
First, a table is generated, and within each row, it contains a dropdown menu. Assume: Rows A, B, C, etc..., and Dropdown selection: 1, 2, & 3
 
If dropdown in Row A selects 2, then I want the selection of dropdowns in rows B & C to dynamically change to 2.
 
And if in Row C user selects 3, then the selection in dropdowns in rows A & B should dynamically change to 3.
 
Does this make sense?  How can I do this?
 
Thanks
 
Jeff in Seattle