<script type="text/javascript">
function changeText(){
 var bill1 = 0;
 var bill = 0;
 var fullbill = 0;
 var fullbill1 = document.getElementById('fullbill1').value;
 var firstAccount = document.getElementById('firstAccount').options[document.getElementById('firstAccount').selectedIndex].value;
 var firstPc = document.getElementById('firstAccount').options[document.getElementById('firstAccount').selectedIndex].id;
 

 bill1 = parseFloat(fullbill1);
 bill1 = bill1-bill1*parseFloat(firstPc)/100;
 bill = bill1;
 fullbill = parseFloat(fullbill1);

 document.getElementById('bill1').innerHTML = bill1;
 document.getElementById('bill').innerHTML = bill;
 document.getElementById('fullbill').innerHTML = fullbill;

}
</script>

<form onsubmit="return false;">
      
    <input class ="value-tt3" type="float" id="fullbill1" name="fullbill1" value="{$post.fullbill1|escape}"  oninput="changeText()"> 
           <select id="firstAccount" name="account1" onchange="changeText()">
        
                     <option value="1" id={$accnpc1} {if $post.account1 == '1'}selected="selected"{/if}>{$accn1} -{$accnpc1}%</option>
                     <option value="2" id={$accnpc2} {if $post.account1 == '2'}selected="selected"{/if}>{$accn2} -{$accnpc2}%</option>
                     <option value="3" id={$accnpc3} {if $post.account1 == '3'}selected="selected"{/if}>{$accn3} -{$accnpc3}%</option>
                     <option value="4" id={$accnpc4} {if $post.account1 == '4'}selected="selected"{/if}>{$accn4} -{$accnpc4}%</option>
                     <option value="5" id={$accnpc5} {if $post.account1 == '5'}selected="selected"{/if}>{$accn5} -{$accnpc5}%</option>
                                                            
          </select> = <output id="bill1">{$bill1}</output> <text>руб</text>

</form>

<input class ="hidden" id="bill1" name="bill1" value="{$bill1}" >