ok Alan, Let's presume you want a polyline that will show up on your paper as being 1mm wide, blue in colour and dashed.
I would create a layer called (for this example) Polyline, set its colour to be 5, it's linetype to Dashed, and its lineweight to be 1mm.
Set the layer created above to be the current layer, ready to be drawn upon.
Then I would draw the polyline.
That's presuming that jonesy is on the right track also.