Can you add a efficiency gain to a asynchronous machine block

I am having great trouble with the SimPowerSystem block Asynchronous Machine, the model is currently ideal and I would like to edit the block to add a gain to give an efficiency loss. This seems simple enough but when i try to add a gain block it tells me im trying to edit a configurable subsystem.

is there anyway around this or do i have to build my own from scratch?

[Chris Knight]

I found a previous question about modifying the asynchronous machine block, it advised taking out the blocks inside the asynchronous block and replacing them with their corresponding blocks in the library. In order to do that you must disable the link to the library however the powersysdomain or ASM block must have a library link to function. So how do you get round this, I dont have permission to edit the library so cannot resolve the link.

I could really use some advice on this.