TAPI Integration to call CRM 2011 Dialog

I need to integrate a telephony solution with CRM, launch a Dialog and pass incoming phone number and a CTI call ref.

Apart from the initial phone call activity record, I only need to create other records (i.e. Contacts, case) as part of the dialog.

I was thinking of using the Dialog URL structure.

http://CRMServer_Name/Org_Name/cs/dialog/rundialog.aspx?DialogId=DialogID&EntityName=EntityLogicalName&ObjectId=EntityObjectId

But can I add a parameter to this URL. i.e. call ref, and pick it up inside the Dialog?

Also any code snippets as examples of how to do this would be greatly apprteciated.

I dont need a full blown add on, these all seem to want to do integrated search and create activitys/contacts etc. which I dont need. None that I have seen mention dialogs.