Hi Dawa,
>
>Just a thought: if you pass the value to populate the textbox as a parameter to the calendar form when the page is popped up in the dialog box, that might get around the problem.
>
>e.g.:
>

>this.Button1.Attributes.Add("onclick", "window.showModalDialog(\"Test.aspx?dDefaultDate=\")"+this.dDefaultDate.ToString());
>

I've dropped the idea of having a modal calendar popup form - Microsoft's calendar control doesn't seem to like showModalDialog. The calendar needs to do a postback whenever the user wants to change month, and this causes an error.