Using v2003

I'll explain as clearly as possible...

I need a formula that will do a count of unique values in a column based on
the condition of two other columns.

i.e. Col A is financial entity id and has duplicates: there may be 5 line
items in entity 556 and 3 line items in entity 444, 5 line items 768, etc.

Col B has the project impact: one of two values, either "Investment" or "ETC"

Col C has the market ID: NE, SE, NW, SW

I need a formula to return the count of unique financial entities that are
Investment in the SE. For example, if the conditions apply to four of the
five 556 entities, the formula would return "1".

Thanks in advance for any guidance! Hope this is enough info.