PowerPoint driven from Excel

[Mihai ZAMFIRESCU]

I want to create from Excel an PP Presentation, create some slides, import
OLE objects (Paste Special as Microsoft Office Excel Worksheet Object or
Picture WMF/EMF/DIB), and to scale the objects(shapes) without distorting'em)
Dim ppt As PowerPoint.Application, sld As PowerPoint.Slide, prs As
PowerPoint.Presentation
Range("A1:B3").Select
Selection.Copy
Set ppt = New PowerPoint.Application
ppt.Visible = True
Set prs = ppt.Presentations.Add(True)
prs.Slides.Add 1, ppLayoutBlank
Set sld = ppt.ActivePresentation.Slides(1)
prs.SaveAs "Sample"
prs.Slides.Add 1, ppLayoutBlank
sld.Name = "qq"
....

Additional questions:
How I can Open an Presentation using Open form?
How I can move to a specific slide and insert there the object wanted?
How I can check if it's already a file with that name (not to override it)?

I use Office 2003 SP2.

Thanks!