No need to feel horrible asking this here.
How one might do this:
In PPT, shapes, slides and even the presentation itself can have an associated tag collection; named string values. For example, assuming a reference to the shape in oSh, you can do:
oSh.Tags.Add "AssociatedSlideId", "293"
In this case, you'd apply this tag to your graph; the 293 would be the SlideID of the slide you want to reference. Each slide has a unique SlideID assigned when it's created; the SlideID won't change when you move the slide around/add/delete slides.
To read the tag from the shape:
Debug.Print oSh.Tags("AssociatedSlideId")
In this case, that'd return "293". Feed that to FindBySlideID to get the SlideIndex of the slide (ie, the ordinal position of the slide in the presentation). Or ask it for SlideNumber if you want the number of the slide that'll appear in number placeholders (usually, but not always the same as slide index).
Debug.Print ActivePresentation.Slides.FindBySlideID(clng("293")).SlideIndex
You might also tag the textbox or other shape that you want to use to hold the reference, then write a function along the lines of:
Function ShapeTaggedWith(oSl as Slide, sTagName as String, sTagValue as String) as Shape
This would iterate through the shapes on slide oSl looking for one with a tag named sTagName, value = sTagValue and return it to the caller if found.
Now you can find the shape that's nominated as your caption for the graph, let's call it, and change its text to match the SlideIndex (or SlideNumber) of the slide the chart's supposed to reference.
Hope that's all moderately clear; if not, that's why the StackOverflow gods gave us comments.
