Spin Button Using Multiple Active Cells

You could use a Forms spin button and assign it to this macro. Press the up button and all cells in the Selection will be incremented by 1, if down, decrimented.
As written it will effect all cells, treating those with text as 0. It can be altered to effect only cells that already have numbers.

Sub Spinner17_Change()
    Dim oneCell As Range
    Dim Incriment As Long
    With ActiveSheet.Shapes(Application.Caller).ControlFormat
        If .Value = 1 Then
            Incriment = -1
        ElseIf .Value = 3 Then
            Incriment = 1
        End If
        .Value = 2
    End With
    For Each oneCell In Selection.Cells
        oneCell = Val(CStr(oneCell.Value)) + Incriment
    Next oneCell
End Sub