First off to debug this I would suggest examining the plcMyStaff
object in which you are adding the control to see if it does in fact contain the control you wish to access.
You should be able to retrieve it from the Page
object that your webform inherits.
Page.FindControl();
// Or you can Iterate through each control to see what the control is called and test for the name you want
foreach (var control in Page.Controls)
{
}