with Richedit1 do
begin
     selstart := perform( EM_LINEINDEX, linenumber, 0 );
     perform( EM_SCROLLCARET, 0, 0 );
end;

{
The EM_LINEINDEX message returns the character index of the first character
on a given line, assigning that to selstart moves the caret to that position.
The control will only automatically scroll the caret into view if it has
the focus, thus the EM_SCROLLCARET.
}