Dim dai As Integer
Dim sho As Integer

Sub ki008()
    Application.OnKey "^{up}", "ki008a"
    Application.OnKey "^{down}", "ki008b"
    Application.OnKey "^{home}", "ki008c"
End Sub
   
Sub ki008a()
    dai = Range("G12").Font.Size
    dai = dai + 2
    Range("G12").Font.Size = dai
    Rows("12").AutoFit
End Sub

Sub ki008b()
    sho = Range("G12").Font.Size
    sho = sho - 2
    If sho = 0 Then
       MsgBox "これ以上縮小出来ません"
       Exit Sub
    End If
    Range("G12").Font.Size = sho
    Rows("12").AutoFit
End Sub

Sub ki008c()
    Range("G12").Font.Size = 10
    Rows("12").AutoFit
End Sub