Conditional Updates

[Kasracer]

In my stored procedure I have a large amount of data that can be updated. What I would like to do is not update anything that is passed into the stored procedure as NULL. How can I accomplish this?

Basically I'm looking for something like this:

UPDATE [MySchema].[MyTable]
	SET
	IF (@MyField IS NOT NULL)
	BEGIN
		MyField  = @ MyField 
	END
	WHERE @UserID = UserID