Custom Task button "Log a Phone Call" in salesforce.com

I'd like to create a custom task button that would create a new activity or task and default subject and a custom field "Activity.Type__c" to "Phone Call" when clicked开发者_运维知识库.

I got as far as defining the button, but need some pointers on what the content source and the actual code should be.

Sample code and/or links to tutorials are greatly appreciated!

You need to set the URL for the button to have GET parameters with Ids matching the fields on the page, and then their values. So, look at the id of the custom field in the HTML, it'll be an 18 character string (e.g. 00ND0000003IyoE). Then set that in the URL with ?00ND0000003IyoE=Phone%20Call. Note: I'm using %20 for the space.