<script language="javascript">
function inc_count1(id)
{
res = document.getElementById(id);
res.value = parseInt(res.value)+1;
}
</script>
<input class="" type="button" value="0" size="12" id="campo1">
<input class="" type="button" value="0" size="12" id="campo2">
<input class="" type=button value=Suma 1 onclick="javascript:inc_count1('campo1','campo2'); ">
![ojotes](http://static.forosdelweb.com/fdwtheme/images/smilies/ojotes.png)