Help incorporating easing into my function

1

i have this function that moves my mc under a mask, when it gets to the higher than the mask its text changes then moves to a position lower then the mask and scrolls back up to its origional position with the updated text. the problem is i need help making it ease instead of just moving with “this._y -=6”

my code:

 
function newProject(g, d, l, c, t) {
 dtext.onEnterFrame = function() {
  this._y -= 6;
  //moving up
  if (this._y < -388) {
   this.description.htmlText = "<font color=\"#CC0000\">+ "+t+"</font><br>"+d+"<br><font color=\"#0099cc\"><a href=\""+l+"\">> Launch It</a></font><br><br><font color=\"#cc0000\">Client:</font> "+c;
   //go below the mask
   this._y = -56;
  }
  if (this._y == -188) {
   delete this["onEnterFrame"];
  }
 };
}