I'm having this Onchange javascript works just fine for HTML, but how can we use RS asp in it?

If RS("MainSelID") = 1 or 3 we would like to disable other select fields. If the user selects other numbers than enble other select fields

Code:
<script language="JavaScript">
    
     function ShowHide(box){
        //disable & enble
       // var SID ='<%=RS("MainSelID")%>'
        
         var SID=box.id="MainS";

        if(SID && box.selectedIndex == '1' || SID && box.selectedIndex == '3'){
            document.getElementById('Select1').disabled=true
            document.getElementById('Select2').disabled=true
        }
        else{
            document.getElementById('Select1').disabled=false
            document.getElementById('Select2').disabled=false
        }
        }
</script>

<form name="theForm" action="Submit.asp" onsubmit="return Validator(this)">

<select id="MainS" onchange="ShowHide(this)">
<option value="0">Main Sectect</option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>

<!--<option selected value=""></option>
   <%Do While Not RS.EOF  %>
       <option value="<%=RS("MainSelID")%>"><%=RS("MainSelID")%></option>
    <%RSValIntent.MoveNext()
    Loop
' RS.close-->
</select>

<select id="Select1">
<option value="0">Select1</option>
<option value="1">1</option>
<option value="2">2</option>
</select>

<select id="Select2">
<option value="0">Select2 me</option>
<option value="1">1</option>
<option value="2">2</option>
</select>


 <br /><br />
      <input type="Submit" value="Submit" name="submit">
</form>