Thanks for the reply. I discovered the call I was looking for. For anyone else interested in this functionality I will post the command to use in the JavaScript section of your ASPX page:
SFX_PostBack('Chart1','C:P,0,1') The first parameter ('Chart') is obviously the name of your chart, thus the name of the object that is initiating the postback. The second parameter ('C:P,0,1') I'm not entirely sure about. It appears the 'C:P' portion is a constant, and it might be an acronym for Chart:Pie, which is the type of chart I'm using. The next part, 0, is the series, and the last part, 1, is the point, which is the index of the region clicked on the chart.