how do you get values from Edit Page: Before Process?

I am trying to get the values of a read only field (acct_num) to store a variable on Edit Page: Before Process
I've tried all of this this for kicks and grins. No dice:
echo "<script>alert('oldvalues - ".$oldvalues["acct_num"]."')</script>";

echo "<script>alert('values - ".$values["acct_num"]."')</script>";

echo "<script>alert('session - ".$_SESSION["acct_num"]."')</script>";

echo "<script>alert('readonly - ".$readonlyfields["acct_num"]."')</script>";

echo "<script>alert('data - ".$data["acct_num"]."')</script>"
It's on a master-detail relationship where on edit all master fields are readonly and the detail fields are editable.
Thanks Much For Your Help!