SUMPRODUCT with conditions

Hi

I have a datatable of employee records with ten columns which is used to calculate employee turnover.

Three of these columns describe the employee - their location, status and employment type.

I have a calculator where the user can enter a filter for each of these columns (into cells B6-D6), and the worksheet calculates the turnover based on another date field (E6).

One of the sumproduct formulas looks like this:

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However, I don't always want to filter on all three conditions, for example, I want the calculation to only filter on Location if location isn't blank. I tried the following but get a value error:

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Can someone help me achieve this?

Cheers
Steve