Determining if a set of sketch relations is unsolvable

How can I check within a macro if the constraints on a pointin a (3D) sketch have become unsolvable? I am creating the pointand constraining it within the macro.

I am using SolidWorks 2009 SP2.1 on Windows Vista SP0. The macro iswritten in VB.NET under VSTA 2005.SolidworksApi macros