Passing variables from a file in a DFIG machine on simulink

Hi,

I have a circuit on simulink which includes a dfig machine. I want that the parameters of the dfig machine, be read from a mfile so I've put variables on the parameters dialog box (like the image bellow)and this results in a "????" machine. Instead, when I put real values on the parameters dialog box the machine appears to be ok. How can I prevent this from happen when I put the variables on the parameters box?