How to automatically run VBA macro on cell change - excel

Question

I have searched extensively for a solution to this but nothing I've tried works automatically. The goal is that anytime text is manually entered in column C, the macro will find the last number used in column CG, increment by 1 if less than 6 and then enter that value on the active row. This works when run manually, but I cannot figure out how to automatically trigger when data is entered in column C.
Sub Counting()
Dim rng As Range
Dim text As String
Dim counterNumber As Integer
Dim counter As Range
Dim ws As Worksheet
Set ws = ActiveWorkbook.Sheets("Sheet1")
Set rng = ws.Cells(ActiveCell.Row, 3)
text = ""
If rng <> text Then
Set counter = rng
Set counter = counter.Offset(-1, 82) 'Finds the last value entered in the Counter column
counterNumber = counter 'Temporary storage for counter number
If counterNumber = 6 Then 'Restarts counting loop
counterNumber = 0
End If
counterNumber = counterNumber + 1 'Increase counter number by 1
Set counter = counter.Offset(1, 0) 'Returns to the active row
counter = counterNumber 'Inputs the updated counter number
End If
End Sub

Answer 1

Please, copy next code in the sheet to be processed code module. To do that, copy the code, right click on the sheet name, choose View Code and paste:
Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Column = 3 Then 'treat only changes in column C:C
Dim counterNumber As Integer, counter As Range, lastR As Long
If Target.Value <> "" Then
Set counter = Me.Range("CG" & Target.row - 1) 'the counter to be updated
counterNumber = counter.Value 'Temporary storage for counter number
If counterNumber = 6 Then 'Restarts counting loop
counterNumber = 0
End If
counterNumber = counterNumber + 1 'Increment counter by 1
counter.Offset(1, 0).Value = counterNumber 'Inputs the incremented number
End If
End If
End Sub

Answer 2

Increment On Cell Change
Standard Module e.g. Module1
Option Explicit
Sub IncrementInColumn( _
ByVal Target As Range)
' Source
Const sCol As String = "C"
Const sNotCriteria As String = ""
' Destination
Const dCol As String = "CG"
Const dCounterMin As Long = 1
Const dCounterMax As Long = 6
Const dNotCriteria As String = "" '***
' Or maybe:
'Const dNotCriteria As Long = 0
Dim ws As Worksheet: Set ws = Target.Worksheet
Dim srg As Range: Set srg = Intersect(Target, ws.Columns(sCol))
If srg Is Nothing Then Exit Sub
Application.ScreenUpdating = False
Application.EnableEvents = False ' to stop retriggering the event procedure
On Error GoTo ClearError ' to enable the settings if something goes wrong
Dim sCell As Range
Dim dCell As Range
Dim dValue As Variant
For Each sCell In srg.Cells
Set dCell = sCell.EntireRow.Columns(dCol)
If CStr(sCell.Value) <> sNotCriteria Then
dValue = dCell.Value
If IsNumeric(dValue) Then
If dValue >= dCounterMax Or dValue < dCounterMin Then
dCell.Value = dCounterMin
Else
dCell.Value = Int(dValue) + 1
End If
Else
dCell.Value = dCounterMin
End If
Else
dCell.Value = dNotCriteria '***
End If
Next sCell
SafeExit:
Application.EnableEvents = True
Application.ScreenUpdating = True
Exit Sub
ClearError:
Debug.Print "Run-time error '" & Err.Number & "': " & Err.Description
Resume SafeExit
End Sub
' Just a Manual Test
Sub IncrementColumnTEST()
If Not TypeName(Selection) = "Range" Then Exit Sub
IncrementInColumn Selection
End Sub
Sheet Module e.g. Sheet1
Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
IncrementInColumn Target
End Sub