how to overwrite a method of inbuild control in c#.net

Question

HI TO ALL,
i am working with c#.net windows application and in one of requrement i need to chage the parameters of a method of the inbuild c#.net control can any one pls help me regarding this...
see the CodeLine-1 below the custom tooltip have method called "show" here it will take only controls as the references to show the  tooltip i need to change the method some thing like codeLine-2

CodeLine-1:CustomTooltip.Show("", control1);
codeLine-2:CustomTooltip.Show("", SomeText);
any one pls help me how achive it...........