Attached is an example book. There are 2 dynamic named ranges using the INDEX/MATCH functions. There are a lot of examples out there using the OFFSET function, but I'm just not a big fan, or convinced it's any better.

So check out the two defined names (Insert -> Names -> Define) MyXdata & MyYdata.

After you define your names like the formulas, the only other thing you need to do, is click on your chart, then click the formula bar, type in a formula similar to this:

=SERIES(,MyXdata,MyYdata,1)

Confirm with enter. Chart will update when sheet is calculated.

Note: Named range formulas are looking down column C and B starting from row 8. It's looking for numerical values. Does this help any?