Target saving pdf with ReportLab

[TheOneElectroni]

Hi everyone.
I'm using ReportLab to generate pdf report from my price list application.
The application runs on windows xp o.s. and is made with tkinter.
What the app make now is that when I press the printPdf button a pdf file with a preset name is created in the current app directory.
What I want to do is that when I press the printPdf button a standard windows dialog windows pops up letting me choose the paht and name for the pdf file. You know, the common behaviour app's return when selecting "save as" for instance.
I've gone trough the user guide and googled without success to find any hint.
Below an excerpt of the RepLab code in the app

def printPS(self):
        def print_(sheet):
            self.getEntry()
            from reportlab.lib.units import inch
            from reportlab.lib.colors import black, white, red, blue
            #to import and set a new truetype font (.ttf) stored in C:\Python25\reportlab\fonts 
            import reportlab.rl_config
            reportlab.rl_config.warnOnMissingFontGlyphs = 0
            from reportlab.pdfbase import pdfmetrics
            from reportlab.pdfbase.ttfonts import TTFont
            pdfmetrics.registerFont(TTFont('Verdana', 'verdana.ttf'))
            ############# end font set-up #############################
            sheet.setTitle("Reciprocating Pump Skids Price List")

            sheet.setFillColor(red)
            sheet.setFont("Verdana", 10)
            sheet.drawString(45, 300, "TOTAL SKID PRICE:")
            sheet.setFillColor(black)
            sheet.drawString(200, 300, str(self.SumTOT) + " EURO")
        sheet = canvas.Canvas("P_List000.pdf", pagesize=portrait(A4))
        print_(sheet)
        sheet.showPage()
        sheet.save()

Thank you for your help!