Sub TEST()
Dim ow As Worksheet
Dim LastColumn As Range
Dim rng1 As Range
Dim TargetCol As Range
Dim SourceCol As Range
Dim LastRow As Long
Dim LastColumn1 As Long
Set ow = ThisWorkbook.Sheets("Overview")
LastColumn1 = ow.Cells(1, ow.Columns.Count).End(xlToLeft).Column
Set rng1 = ow.Cells.Find("[1]", LookIn:=xlValues)
ow.Range(rng1, ow.Cells(ow.Rows.Count, rng1.Column)).EntireColumn.Insert
Set TargetCol = rng1.Offset(0, -1)
Set SourceCol = rng1.Offset(0, -2)
LastRow = ow.Cells(ow.Rows.Count, SourceCol.Column).End(xlUp).Row
SourceCol.AutoFill Destination:=TargetCol, Type:=xlFillDefault
TargetCol.Formula = "=" & SourceCol.Address
End Sub