For the sub below, instead of msgbox, I would like to write
all results into say, B2 down on the sheet. How? Thanks.

Sub findmissingnumbersinlist()
mc = 1 'for col A
For i = 2 To Cells(Rows.Count, mc).End(xlUp).Row - 1
If Cells(i + 1, mc) < Cells(i, mc) + 1 Then
MsgBox "Missing " & Cells(i, mc) + 1 & " at row " & i + 1
End If
Next i
End Sub