<div>
  <div class="box01">
    箱
  </div>
  <div class="box02">
    箱
  </div>
</div>

div{
  position: relative;
  text-align: center;
}
.box01,.box02{
  width: 150px;
}
.box01{
  position: absolute;
  top: 0;
  left: 0;
  margin-left: 20px;
  background-color: lightblue;
}
.box02{
  position: absolute;
  top: 0;
  left: 170px;
  margin-left: 50px;/* この値を変更するとbox02が動きます */
  background-color: pink;
}