Hi
You can sketch a line then variable section sweep for a line that has variable angle function(for example sd5=360*trajpar*no_turns) done. Then go to Insert--model graph----graph.
give it a name(for example var). Draw a nonlinear graphs at both ends but linear in the middle, add a coordinate system then save it.Move the graph feature from the tree before the variable section sweep. Go back to the line where you put the relation (sd5) modify it to become (sd5=360*evalgraph("var",trajpar)*no_turns).