I have done something very similar for one of our clients. Here's a brief idea of what I do:

I have a userform for the user to input data, which puts the entered data into the required places in the PPT file. Each shape in the presentation which will receive data is identified by an added 'tag' to the shape, e.g.
('Identifier' is the name of the tag that identifies the shape as a target, and 'CurrentSalesChart' is the name of the specific shape.)

First, I loop through every shape in the presentation (on slides and master templates) to locate these tagged shapes. Then I show the user the userForm for data entry, and after the user enters their data, they click the 'apply' button on the form, which sets the data into the various charts and tables that were located, and saves the presentation under the account name and date.