Pulling values across entities during dialog steps

Hi All,

I have a requirement to populate custom form fields on closure of a case entity from a dialog process.

Have followed this blog to some degree....
http://www.powerobjects.com/blog/2012/02/02/use-a-dialog-process-in-microsoft-dynamics-crm-to-replace-the-case-resolution-form/

However during steps of the dialog i need to pull data from another custom entity where the relationship between case and "casedetails" is 1:n.

If i add a step to update the case entity the "Look for" related entities dropdown does not contain "casedetails" so im stuck as to how to pull the fields.

Any guidance would be greatly appreciated...