Assigning variable values to Values and XValues

Hello, I'm new and I am trying to understand the syntax or data types when assigning a range to XValues and Values in the SeriesCollection.

Consider this code which is from a recorded macro and works just fine:

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Now I am trying to replace the constant for Values and XValues with a string value:

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The code breaks at the red highlighted line even though in the watch window the string value of ValueString is identical to "='1YearByProduct'!$B$3:$M$3"

Please advise. I'm puzzled. I appreciate your input.