You have a field in your database that you want to always be lowercase.
Try the following in your JavaScript:
<SCRIPT LANGUAGE="JavaScript">
function ChangeCase()
{
var strVariable = document.MyForm.txt_myfield.value;
strVariable = strVariable.toLowerCase( );
document.MyForm.txt_myfield.value = strVariable;
}
// End --></script>
To change the case to upper simply use toUpperCase() in your function above.
Hope this helps.