Have object - want that user sees selection

Dear experts,

I'm down in the object store and have found a marker. I want that the user sees in the document, what I have found.

The problem is: how to come from an object to a TextSelection and TextLocation? All I have found goes the other way round.

currentMarker = GetFirstMarker (doc, "#calc"); // this does its job
doc.TextSelecton = currentMarker;              // no error, no effect
doc.ScrollToText(...);                         // requires TextLocation

I have studied more than one diagram of the DOM but still don't see through the fog.

Klaus