Preventing user from using webpage until it is fully loaded

Hi there Experts,

I would like to know what is the best way to prevent the user from using the webpage until it fully loaded.

On one of my pages, I have an iframe that loads just before the </body> tag.
On the same page I have a Javascript Calender that is activated by click on a image on the page, which calls the iframe.
(The Javascript calender is displayed in an iframe)

I have found that sometimes people click on the image to call the calender, BEFORE the <iframe>....... </iframe> code has been executed.

Is there a way to force the user to wait until the page is fully loaded?

Here is some source code:

// the javascript calender display in the iframe and insert the date value into the text box for Arrival Date//
           
<input type="text" id="RoomOneArrivalDate" name="RoomOneArrivalDate" size="12" onfocus="this.blur()" readonly>
 <a onclick="gfPop.fStartPop(document.gbi.RoomOneArrivalDate,document.gbi.RoomOneDepartureDate);return false;"
      onMouseOver="javascript:check_status()" HIDEFOCUS  href="javascript:void(0)">
     <img name="popcal" align="absbottom" src="calbtn.gif" width="34" height="22" border="0" alt="">
 </a>
.
.
.
.
.
// the javascript calender display in the iframe and insert the date value into the text box for Departure Date//

<input type="text" name="RoomOneDepartureDate" id="RoomOneDepartureDate" size="12" onfocus="this.blur()" readonly>
 <a onclick="gfPop.fEndPop(document.gbi.RoomOneArrivalDate,document.gbi.RoomOneDepartureDate);return false;"
       onMouseOver="javascript:check_status()" HIDEFOCUS href="javascript:void(0)">
       <img name="popcal" align="absbottom" src="calbtn.gif" width="34" height="22" border="0" alt="">
 </a>
.
.
.
.
<iframe width=174 height=189 name="gToday:normal:agenda.js" id="gToday:normal:agenda.js" src="ipopeng.htm" scrolling="no" frameborder="0" style="visibility:visible; z-index:999; position:absolute; left:-500px; top:0px;">
</iframe>

</body>