Dim Max As Integer
Dim NonBlank As Integer
Dim MyRange As Range

Max = ThisWorkbook.Sheets("YourSheet").Cells(Rows.Count, YourCol).End(xlUp).Row
Set MyRange = ThisWorkbook.Sheets("YourSheet").Range("C1:C" & Max)
NonBlank = WorksheetFunction.CountA(MyRange)
Set MyRange = Nothing