<script language="javascript"> 
var nereye = 'sifre'; 
function tusGir(tus){ 
   document.getElementById(nereye).value = document.getElementById(nereye).value +  
tus ; 
} 
</script> 

<table > 
<tr> 
<td colspan="3" align="center"> 
<input type="text" name="sifre" size="22"  ></td> 
</tr> 
<tr> 
<td><input type="button" value="  1  " onclick = "tusGir('1');"></td> 
<td><input type="Button" value="  2  "  onclick = "tusGir('2');"></td> 
<td><input type="Button" value="  3  "  onclick = "tusGir('3');"></td> 
</tr> 
</table>