Some hints for you to find out how to do it:

• The function in VBA you are looking for is (most likely) AddOLEObject.
• In Powerpoint, go to the Developer Ribbon.
• Start VBA (Alt F11).
• In VBA, start Object Browser (F2).
• Type addoleobject in the search field and click the search button.
• Check the function call and work out how to specify a filename instead of a classname in contrast to pie chart in powerpoint.

From here, it might involve a bit of experimentation, but that is the same for me as well...