<form action="<?php echo $editFormAction; ?>" method="post" name="form1" id="form1">
  <table>
    <tr valign="baseline">
      <td nowrap="nowrap" align="right">Price:</td>
      <td><label>
        <select name="price" id="price">
          <option value="price1">price1</option>
          <option value="price2">price2</option>
        </select>
      </label></td>
    </tr>
    <tr valign="baseline">
      <td nowrap="nowrap" align="right">Course:</td>
      <td><label>
        <select name="course" id="course">
          <option value="course1">course1</option>
          <option value="course2">course2</option>
        </select>
      </label></td>
    </tr>
  </table>
</form>

var pr = document.getElementById("price");
var co = document.getElementById("course");

pr.onchange = function() {
  if(this.value == "price1")
  {
      co.selectedIndex = 0;
  }
    if(this.value == "price2")
  {
      co.selectedIndex = 1;
  }
}

co.onchange = function() {
  if(this.value == "course1")
  {
      pr.selectedIndex = 0;
  }
    if(this.value == "course2")
  {
      pr.selectedIndex = 1;
  }
}