I need to create a multi-dimensional process model. The opening screen has the highest-level process chart (using shapes), let's say ten steps. In each shape there would be a small circle shape which the user would click and then be taken to the second-level process chart (over-layering the previous screen), which in turn would have hyperlinks to the third level, etc. In each sub-level there would be hyperlinks to the previous chart, or the highest level chart. How would I create this in Excel? Or, should I use Visio and convert it to Excel? Is there a name given to this kind of modeling?

Your entire thread reads to me a Visio is the right program to use.

Not sure why you would ever then take what you make in Visio and transfer it to Excel.

Use the right program for the right job. Visio in this case.