Not sure I understand what you want to do.

But if your asking if you can assign the Data Field property at runtime then the answer is, Yes.

rptAssessment.Sections("users_header").Controls.Item("name").DataField = "fullname"

"fullname" is a field from the Data Member property

I usually do this in Datareport "report_initialize" event.
You can also set the Datasource, Data Member properties and many other things.

Good Luck