How to INDEX sparse array?

Question

How can I INDEX a sparse array without resorting to VBA?

By "sparse", I mean a mix of elements with FALSE values and other values.  I want to ignore the FALSE values when applying the index.

The situation arises in the following array formula, for example (assume C1>=2):

=INDEX(IF(A1:A10=1,B1:B10),INT(C1/2))

where C1 is the array formula =COUNT(IF(A1:A10=1,B1:B10)).

In actual usage, I do not always want C1/2.  And the selection criteria for the array might not always be one simple criterion.

To clarify, I want 3 from the following formula:

=INDEX({1,FALSE,3,4},2)

The following VBA function demonstrates the desired behavior:

Function myIndex(a, n)

Dim i As Long, k As Long

myIndex = CVErr(xlErrNum)

If TypeName(a) = "Variant()" Then

   'If UBound(a, 2) <> 1 Then exit function

   For i = 1 To UBound(a, 1)

      If a(i) <> False Then

         k = k + 1

         If k = n Then myIndex = a(i): Exit Function

      End If

   Next

End If

End Function