//こんな感じかね。
var fstr="【";
var estr="●";

erabu(fstr,estr);

function erabu(fstr,estr){
if(!document.selection.Find(fstr,eeFindPrevious))return;
document.selection.Collapse();
var xsPos = document.selection.GetActivePointX( eePosLogical );
var ysPos = document.selection.GetActivePointY( eePosLogical );
if(!document.selection.Find(estr,eeFindNext))return;
document.HighlightFind=false;
document.selection.CharLeft(0,estr.length);
var xePos = document.selection.GetActivePointX( eePosLogical );
var yePos = document.selection.GetActivePointY( eePosLogical );
document.selection.SetAnchorPoint( eePosLogical, xsPos, ysPos );
document.selection.SetActivePoint( eePosLogical, xePos, yePos, 1 );
}