How to hide content of a

I have a webform that has some of the content in asp tables.  I would like to hide the content of some of the TableCells until an event occurs.   I've tried naming the TableCell and setting visible="false" ...
<asp:TableCell ID="CNDetailCell" Visible="false">
...and setting the cell ID to visible=true in the code behind when the event has occurred...
CNDetailCell.visible = true;
...but get exception...
'System.Web.UI.WebControls.TableCell' does no ...