Hi NWill,
Our DBXL Web Service supports your scenario today. We have a separate "system" form that keeps assignment information (i.e. the history of your user assignments). Anyway, we can show you a demo if you are interested. We use the taskpane to show workflow status, taxonomy info and history of assignments.
You can also use SharePoint workflows and InfoPath 2007. However, the users will have to go to SharePoint to see history.
If you would like to build this from scratch, I recommend using a database and a separate table with a row for assignment (with columns: ID, assignee, assignedTo, date, time, status). To submit this data will require a separate Web Service to write the values, but you can do it.
Of course, 10 minutes and DBXL and you are done, but if you like to spend lots of time and money, go for it.