Count unique values (ignore duplicates) with multiple other column criteria

Hi All,

I need to count the number of unique value in a column, but this will depend on certain criteria been met in several other columns first.

In the attached i have a 'Full Data' sheet which is where i all the data i am trying to count exists. The 'Summary' sheet is where i am trying to calculate/count the number of unique values.

I have positions (Summary - a5:a22) that i want to calculate the number of staff currently in that position. I also want to be able to restrict the 'Dept' - (Full Data - E:E) (additional department not included in this worksheet) and the 'payrun Number' (Full Data - D:D).

basically, count the number of "Chef" at Dept 15 and in payrun number 143 (but department and payrun number will continue to vary).

Thanks in advance to anyone that can help.