Compare User Imputed Data to Pivot Table

I am attempting to use an "IF" function to compare a data value from an inventory list in a pivot table with a user editable cell next to the pivot(for a physical inventory count).

=IF(GETPIVOTDATA("CurrentInventoryQuantity",B8)=G8,TRUE,FALSE)

This code returns an #REF! error.

I have to store the inventory data in a pivot so that it can dynamically add new rows as needed.

Any tips on how to get Excel to compare the data?