Interactive Custom Report Item

I'm looking at creating a custom report item which will allow me to input data into a textbox on the rendered report and dynamically update a textbox or another custom report item once I leave focus of that initial textbox. Is there a way to accomplish this? I have read that you can only create CRIs which use "graphic elements and images". Is that a true statement?

The reason why I don't want to have the initial value as a parameter is becuase the client doesn't want to have to click "View Report" everytime they want to see an updated value.

Thanks,
--Josh