int pascal CheckRadioButton(HDLG hDlg, int idFirst, int idLast, int idItem)

  This function checks a radio button which is contained within a
group of radio buttons. When this button is checked, all the other
radio buttons in that group will have their checks removed.

Parameters
  hDlg is the handle of the dialog box which contains the specified control.
  idFirst and idLast are the ids of the first and last radio buttons
   in the radio button group which contains idItem. All radio buttons
   within the group must have identifiers which are consecutively
   numbered from idFirst to idLast.
  idItem is the id of the radio button which we want to check.

Returns
  TRUE if the operation was successful, FALSE if not.