You can throw this script into the footer of your ranking question ...
<script>
window.onload=function()
{
document.mainform.Q1_1.value='100';
}
</script>
This would preset Q1_1 (the 1st item in Q1) to "100".
You can also tweak your script by using the QuestionName function also ...
<script>
window.onload=function()
{
document.mainform.[%QuestionName()%]_1.value='100';
}
</script>