OFFSET FUNCTIONS IN A CHART, FORMULA ERROR KEEPS COMING UP.

[Guest]

I want to link this to a scroll bar so i can view only 10 weeks at a time but
i keep getting an error msg when i try to input my name defined cells int he
source data of the chart
MY OFFSET FORMULAS ARE AS FOLLOWS,
NAME defined: DATA (=OFFSET(Sheet1!$B$3,0,COUNTA(Sheet1!$B$3:$P$3)-16,1,16)
NAME DEFINE : WEEKS =OFFSET(Sheet1!$B$2,0,COUNTA(Sheet1!$B$2:$R$2)-16,1,16)

When I put the 'data' or 'weeks' in the chart source i keep getting this
error msg,
"A formula in this worksheeet contains one or more invalide references.
Verify that your formula contains a valid path, workbook, range name, and
cell reference."

Any suggestion about why or my error with the offset formula?

 

[Guest]

This part

COUNTA(Sheet1!$B$3:$P$3)-16

needs to be > 0 to work. I'm just guessing the result is < = 0.