Looks like you are willing to modify by AutoLISP a custom entity of MEP – I’m not aware that SPACE entity is available in Vanilla AutoCAD. For this reason will be easy to get support from someone using MEP too.
Just to see that the associated list of this entity can be accessed and modified, please paste the code below to your command line, select a SPACE item and post here the result. Thank you.
Code:(entget (car (entsel)))