Without your spreadsheet attached to assist, the best I can do is provide an example.

I have defined dynamic named ranges using OFFSET. These ranges are named DATES_COLUMN and YCOL_1.
Under the 'Select Chart Data' option after right-clicking the graph, you can select to edit a range. Here you can define the Series name, Series X Value Array and Series Y Value Array

My X Value Array is:
='12-30-2014-092756.xlsx'!DATES_COLUMN
My Y Value Array is:
='12-30-2014-092756.xlsx'!YCOL_1
I believe the workbook name is required when referencing a named range.

If you are still unable to get this to work, please post a spreadsheet and attach it to your post using 'Go Advanced'