A sample file would generally help in these instances but I wonder if perhaps something along the lines of the below would work for you ?
The above should be placed in the Sheet object that contains the named range NPI_GroupOffset - to ensure this is placed correctly right click on the tab name in XL select View Code and paste above into resulting window - thereafter ensure Macros are enabled. As you alter the content of the named range you should find the PT Field is filtered according to the content of the named range.
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