ASP.NET WebUserControl Enhancement

Currently have a working C# ASP.NET WebUserControl consisting of 2 graphics (downarrow and a notepad icon), with a TextBox control. The downarrow when pressed, expands the textbox xx rows (default of 20), the notepad icon when pressed inserted the users intials and current Date. The links work with Javascript inserted on the Page Load event. Properties assigned to the control tell it whether to be ReadOnly or to allow a user to type into it. Problem is that during postback, the ReadOnly property does not change the TextBox to ReadOnly