Could you please upload a sample of your work book to a free file sharing site such as Drop Box and then post the link to your file back here. Be careful with any sensitive data.
It would be easier for us to run some tests in your sample in order to determine how to best solve this for you.
Please also supply us with a clear and precise explanation of what you would like to do with inputs and expected results.
Which column will be the key to firing the update process?