With Sheets("A")
.Range("j1").EntireColumn.Insert xlToLeft
.Range("j2").FormulaR1C1 = "=RC[-2]&"" - ""&RC[-1]"
.Range("j2").AutoFill Destination:=.Range("j2:j5000"), Type:=xlFillDefault
.Columns("j:j").Copy
.Columns("j:j").PasteSpecial Paste:=xlPasteValues
Application.CutCopyMode = 0
End With