Gist based on StackOverflow.com question - https://stackoverflow.com/questions/59274383/combine-two-vba-codes-into-one

TwoChangeEventsInOne.vb

Private Sub Worksheet_Change(ByVal target As Range)

    FirstCode target
    SecondCode target

End Sub

Private Sub FirstCode(ByVal target As Range)
  Dim Item As String
  Dim SearchRange As Range
  Dim rFound As Range

  'Don't run the macro if:
  'Target is not a single cell:
  If Target.Cells.Count > 1 Then Exit Sub
  'or Target belongs to the A1.CurrentRegion:
  If Not Intersect(Target, Range("A1").CurrentRegion) Is Nothing Then Exit Sub

  'Avoid the endless loop:
  Application.EnableEvents = False

  'Looks for matches from the here first:
  Set SearchRange = Range("A1:A" & Range("A1").CurrentRegion.Rows.Count)

  Item = Target.Value

  'Clears the Target:
  Target.Value = ""

  If Application.WorksheetFunction.CountIf(SearchRange, Item) > 0 Then
  'There's a match already:
  Set rFound = Columns(1).Find(What:=Item, After:=Cells(1, 1) _
  , LookIn:=xlValues, LookAt:=xlPart, SearchOrder:=xlByRows _
  , SearchDirection:=xlNext, MatchCase:=False, SearchFormat:=False)
  'Adds one to the Quantity:
  rFound.Offset(0, 2).Value = rFound.Offset(0, 2).Value + 1

  Else

  'Writes the value for the Barcode-list:
  Range("A" & SearchRange.Rows.Count + 1).Value = Item

  'Looks for the match from sheet "Inventory" column A
  With Sheets("Inventory")
  Set rFound = .Columns(1).Find(What:=Item, After:=.Cells(1, 1) _
  , LookIn:=xlValues, LookAt:=xlPart, SearchOrder:=xlByRows _
  , SearchDirection:=xlNext, MatchCase:=False, SearchFormat:=False)

  On Error GoTo 0

  If Not rFound Is Nothing Then
  'Writes the Product Name and puts 1 to the Quantity column:
  Range("B" & SearchRange.Rows.Count + 1).Value = rFound.Offset(0, 1).Value
  Range("C" & SearchRange.Rows.Count + 1).Value = 1
  End If
  End With
  End If

  'Enable the Events again:
  Application.EnableEvents = True

End Sub

Private Sub SecondCode(ByVal target As Range)
  If Target.Column <> 3 Then Exit Sub
  If Target.Cells.Count > 1 Then Exit Sub
  With Target.Offset(0, 3)
  .Value = Now
  .NumberFormat = "DD/MM/YYYY"
  End With
End Sub