Each x- or y- range for each series must be from a single worksheet.
You can combine different sheets for different sheets or different
ranges for x- and y- ranges for a single series but not multiple
worksheet ranges in a single x- or y- range.

Consider consolidating the data into a single worksheet and then
plotting that consolidated range.

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Tushar Mehta
www.tushar-mehta.com
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In article ,
says...
I am trying to use ranges from several pages in one chart. When I set the
source data to: =Sheet1!$A$2:$O$2+Sheet2!$A$3:$K$3

I get the following error: Reference is not valid

HELP, what am I doing wrong?