AFAIK, Entrust e-grid is not one of the RADIUS vendors we worked with when this RADIUS feature was added. In my article VMware View 5.1 RADIUS Authentication Setup I list some of the vendors that have known working solutions with View. Many other vendors will also work with View.
I could be wrong, but I think the problem here is that there is no way in View (currently) of prompting the user for the grid positions that they need to use to enter the grid values in the text input screen. It might be that this part is done in a RADIUS Access-Challenge and it could be a matter of displaying the message in the Access-Challenge to the user. It would then be necessary for the user to enter the grid values in the challenge input field to complete the authentication process. Without doing this level of integration, it can't work.
In all cases where RADIUS integration with View is required, I'd encourage you to contact the RADIUS vendor to ask specifically what they have for VMware View integration information. I list some of the links to this material from several vendors in my article. Many vendors publish specific guides on how to set up View, and have tested interoperability details that they can share with you.
Mark