adding a filter to a measure

hi everyone

i have the following working measure

Measure 9 : = SUM(Financials[GlobalRolling12MTH]) / COUNT(Projects[ProjectName])

(so financials is a table, globalrolling12MTH is a column in that table, projects is a table, project name is a column in that table)

- this formula works and gives me the number figure i need.. however

now i need to add a filter to this figure..

i have another table called NPDMetrics, in this table is a column called prioritisation (choice field of gold, silver bronze)

so how can i use the above formula and then add "where prioritisation = gold" "where prioritisation = silver" "where prioritisation = bronze". i assume three meausures and thats ok

please help :(

thanks

Nikki