Loop through mySQL columns and average the values

[digitalShaman]

stored procedures are not my bag and i have done only very Little with mySQL.
But maybe the following gets you started even though it is MSSQl Syntax:

	declare @dtOldest as datetime 
	set @dtOldest= (select min(dt) from tbl)
	while datediff(hour,@dtOldest,getdate())>=4
		begin
			declare @dtNewOldest as datetime=dateadd(minute,1,@dtOldest)
			INSERT INTO tblNew 
				SELECT min(dt),avg(Value1),avg(Value2)
				FROM tbl
				WHERE dt<=@dtNewOldest
			DELETE FROM tbl WHERE dt<=@dtNewOldest
			SET @dtOldest=@dtNewOldest
		end

its untested so i am not sure if it really does what is asked.