Using 'Convert to Solid' Object in Matlab Livelink: specifying a selection

I am scripting a simulation using the Matlab Livelink interface. I am able to build a geometry using and import object surface combined with parametric surfaces and I would like to convert this into a solid object.

I have already tested this through the GUI and it works fine. The geometry generated through the script also looks fine (i.e. edges match up).

However the problem is how to "feed" a selection to the convert to solid object:

          csol1 = geom1.feature.create('csol1','ConvertToSolid');

I can see that there is nothing selected when I type the following command in Matlab: csol1.selection('input')