why don't u expose a read-only property (TextBoxValue) with the value of the TextBox and once you find the UserControl, just select the UserControl.TextBoxValue :
UserControl
public int TextBoxValue
{
get { return this.txtBox.Text; }
}
ASPX
foreach (Control c in form1.Controls)
{
if (c.GetType ( ).Name.ToLower ( ) == "webusercontrol_ascx")
{
UserControl uc = (UserControl)c;
if(uc != null)
{
Response.Write ( "Controlvalue: " + uc.TextBoxValue + "" );
}
}
}
[edit] code blocks added [/edit]