Modify the TableHeaderContainer style element. The STYLE statement with the FROM option specified creates the style element TableHeaderContainer which inherits all of its style elements and style attributes from the instance of TableHeaderContainer in the Styles.RTF style. The BORDERBOTTOMWIDTH=, BORDERBOTTOMCOLOR=, and BORDERBOTTOMSTYLE= style attributes specify the width, color, and line style of the bottom border of the table header.

   style TableHeaderContainer from TableHeaderContainer /
      borderbottomwidth=12 
      borderbottomcolor=blue 
      borderbottomstyle=dotted;