Attribute VB_Name = "testsub2"
Sub テスト()
    Dim str As String

    str = "こんにちは"
    Call setCellValue(str)

    Range("A2").Value = str

End Sub

Sub setCellValue(ByVal str As String)

    str = str & "お元気ですか"
    Range("A1").Value = str

End Sub