How to define and edit default value for variable in scheduled transactions

[Svetoslav Trochev]

Hi Everyone, 
 
I am learning how to use GnuCash right now. I am switching from Quicken, so I need to break some old habits. Currently I am working on Scheduled transactions. So far I have learn how to create a new scheduled transaction and I think I understand all options. I even was able to create scheduled transaction with simple formula, but I can't find out how to set default value for my variables. Here is the example what I am trying to do: 
 
1. I am receiving a bill from My Power Company. It usually arrives some time in the first week of the month and it is due on the same day each month. For example: 2009-04-28. 
2. I have created scheduled transaction that will debit my "Checking Account" by "Amount" and credit my "Utility Account" by the same "Amount" every month on 28th. 
3. I schedule this transaction to remind me 7 days in advance of the Due day. 
 
This part works ok. When the reminded is due I can see the transaction in "Since Last Run" window and it prompts me for the value of the "Amount" variable. 
 
What I would want is to be able to update my "Amount" when I receive the bill from the power company and this value to be used as default value when the transaction is due. 
 
Can the GnuCash work that way and if not how you, more experienced users, would recommend to me to handle the variable utility bill? 
 
Thank you, 
SAL-e