Unable to Get Default value for Text Box to Display

I have an SDI project with a menu on the left hand side so the user can enter information such as data filename and choose the number of seconds to run a test. I have created an SDI project and follow the link : http://www.functionx.com/visualc/dialogboxes/dialogbars.htm to create a dialog bar on the left hand side of the frame. On the dialog bar, I have a text box and a push button. Unfortunately, I can not enter any information into the text box b/c the add variable option on the textbox is grayed out. I have tried using SetDlgItemText(IDC_MENU_EDIT, _T("test")); to set the text box to test but nothing show up. Does anyone know how to create a SDI project with a dialog box on the left hand side of the frame? The SDI interface will be used to display a graph while the dialog on the right will be used to gather info from the user. Any helps would be appreciated. Thanks.