Let me see if I can explain this clearly.

I wanted to create a block with an attribute that has a field that will be linked to a polyline to reflect its area property. So, I created the block with the attribute field. While creating the block (i.e. while in the dwg file), I drew a polyline and linked the field to to it to confirm that the field worked properly. Then I erased the polyline (since I don't want it to be part of the block's definition), thus breaking the link between the field and the pline it was associated to.

Now, when I use the block, I would like to associate its attribute to an existing polyline. How would I do this via Autolisp? In one sense, I am simply updating the attribute value, but the value is coming as a result of associating the attribute field to a polyline. So, is there a way to edit the attribute and point the field to an object?