Sum only those that are visible - excel

Question

Recently, I have been trying to code a VBA to assist me in summing a column and divide by counter to get average. However, I have a new requirement that is it is only going to sum up those that are visible. Any idea on how should I proceed? Below is my code,
Sub test3()
Dim FinalRow As Long
Dim Row As Long
Dim counter As Integer
Dim total As Double
counter = 3
total = 0
Dim i As Double
FinalRow = Range("C65536").End(xlUp).Row
For Row = 3 To FinalRow
If Not IsEmpty(ActiveSheet.Cells(counter, "C")) And Not IsEmpty(ActiveSheet.Cells(Row + 1, "C")) Then
If ActiveSheet.Cells(counter, "B").Value = True Then
ActiveSheet.Cells(Row, "M").Value = 100
For i = counter To Row
If IsEmpty(ActiveSheet.Cells(i, "F")) Then
With ActiveSheet.Cells(i, "F")
.Value = Now
.NumberFormat = "dd/mm/yy"
If (.Value - .Offset(0, 2).Value) >= 0 Then
.Font.color = vbRed
Else
.Font.color = vbBlack
End If
End With
End If
Next i
End If
If (ActiveSheet.Cells(Row, "L").Value = 100) Then
For i = counter To Row
If IsEmpty(ActiveSheet.Cells(i, "F")) Then
With ActiveSheet.Cells(i, "F")
.Value = Now
.NumberFormat = "dd/mm/yy"
If (.Value - .Offset(0, 2).Value) >= 0 Then
.Font.color = vbRed
Else
.Font.color = vbBlack
End If
End With
End If
Next i
End If
If Not (ActiveSheet.Cells(counter, "B").Value) = True Then
ActiveSheet.Cells(counter, "M").Value = (Application.Sum(Range(ActiveSheet.Cells(counter, "L"), ActiveSheet.Cells(Row, "L")))) / (Row + 1 - counter)
End If
counter = Row + 1
End If
Next
End Sub

Answer 1

This testcode works for me, just change it as you need it:
Sub TestSumme()
Dim Summe As Long
Summe = Application.WorksheetFunction.Sum(ThisWorkbook.Sheets(1).Range("A1:A6").SpecialCells(xlCellTypeVisible))
MsgBox (Summe)
End Sub