Currently, I am using:

Sheet3.Range("A1:A10000").AdvancedFilter _
Action:=xlFilterCopy, _
CopyToRange:=Sheet2.Range("A1"), _
Unique:=True

This generates a list of the unique values from my source list. While I can
get to my real end result through several additional steps, I suspect that
I'm underutilizing AdvancedFilter, and am hoping for a few pointers on how to
get it to return some more specific information.

Specifically,
(1) I do have a criteria that I'd like to use without placing it in a cell
range (Select unique values from A1:A10000 where the corresponding value in
Column K is '4'). It appears that I can put the value 4 in a cell and
reference it, but can I just use a variable which is =4? If so, what is the
appropriate syntax?
e.g.,
CriteriaRange:= (Sheet1.range(K:K).value = 4)

(2) Ultimately, what I really want is a count of the unique values that meet
my criteria, so can I use a Count against the returned range, without sending
it to a physical page location? Perhaps I can make a named range that
references an array instead of a range, and use that to generate a count in a
second step?

Initially I was using formulas to get my unique counts, but using a
sumproduct formula (actually, several dozen of them) against an array this
large was just taking too long, and initial tests with AdvancedFilter
indicated it would be much faster.

I appreciate any syntax hints with the AdvancedFilter, or even confirmation
on whether or not what I'm attempting is even possible with AdvancedFilter.

My backup option is to just loop the page and sort the data into a 2D array
(while keeping track of whether each value is unique), but AdvancedFilter
seemed like a more direct option (no loops, etc)

Thank you,
Keith