Formula to count occurrences in a filtered column
 

I have a spreadsheet that uses a fairly complicated formula to count the number of occurrences of a value in a filtered column. Here is the current formula:

[B2]=SUMPRODUCT( SUBTOTAL( 3, OFFSET( NamedRange, ROW(NamedRange) - MIN( ROW( NamedRange )),,1)), 0+(NamedRange=A2))

I'm trying to figure out if there's a more efficient way to do this, as the spreadsheet is very slow and I think that this formula along with many like it are a large part of the problem.

Any suggestions?

Phil.