自前のエクステンションでVBScriptを利用しています。

サンプル

GraphicsWindow.BackgroundColor = "yellow"
button = Controls.AddButton("caption", 300, 200)
Controls.SetButtonCaption(button, "file")
Controls.ButtonClicked = onclick
WC = Text.GetCharacter(34)
CRLF = Text.GetCharacter(13) + Text.GetCharacter(10)
code = ""
code = code + "Function setup(a)" + CRLF
code = code + "  With CreateObject(" + WC + "SAFRCFileDlg.FileOpen" + WC + ") " + CRLF
code = code + "    If .OpenFileOpenDlg Then setup = .FileName" + CRLF
code = code + "  End With" + CRLF
code = code + "End Function" + CRLF

Sub onclick
  a = Class1.VBSrun(code)
  GraphicsWindow.ShowMessage(a, "path")
EndSub