Modal PopUP within a DetailsView

Hello there.
I am hoping someone has done what I am trying to do and can explain to me how I can achieve my goal.

I am trying to use the model popup control within a DetailsView. I have added a template field within the detailsview and also a button next to the field. I am trying to set it up so when I press the button the modal pops up ,which allows me to add some info into a textbox and then postback to a db.

I have added a panel and called it pnlUpdate, in the panel I have added 2 buttons (Insert & cancel) + the txtbox. When I look at the buttons properties and try selecting the popUpControlID to be pnlUpdate from the dropdown its not there.

Has anyone run into this problem?

Thanks

Shane

Sorry to bump this back up to the top but I still can't seem to resolve this myself