Average Dynamic Data But Exclude Zeros

I use a SQL query to export a subset of data from our server. After manipulating the received data I need to Average one column that has been sorted into a number of blocks consisting of variable numbers of rows and post the result to the ajacent cell. I have tried the Countif worksheet function but am unable to resove the syntax problem.

Sub SumBlock()
Dim First_Row As Long
Dim Last_Row As Long
Dim iTotalRows As Long
Dim iCount As Long
iTotalRows = Range("A65536").End(xlUp).Row
First_Row = 2
Do While Last_Row < iTotalRows - 1
Last_Row = ActiveSheet.Range("j" & First_Row).End(xlDown).Row
iCount = Application.WorksheetFunction.CountIf(Range("J" & First_Row), ("J " & Last_Row), ">0")
ActiveSheet.Range("K" & Last_Row + 1).Formula = "=Sum(J" & First_Row & ":J" & Last_Row & ")/iCount"
First_Row = Last_Row + 2
Loop
End Sub