Need an apex trigger

I need to update a field on the account object whenever a task is created via the Email BCC to Salesforce function. From what I understand this is only possible with an apex trigger. Here is an example of the problem I'm facing and the solution I need...I just don't know how to write the trigger: http://succeedwithsalesforce.com/updating-related-record-via-apex-when-using-send-an-email-button-under-activity-history/