CompactLogix program execution

hi all,

under the continuous task, i have 3 programs.
the first one copy a value from HMI linked tag to a tag called new_val,
the third program copy a value from the same HMI linked tag to a another tag called old_value. i compare new_val and old_value tags using a
CMP instruction to detect a change in the HMI linked tag in the second program

is it a correct way to do?
how do i always make sure the three programs executes one after other, first second and third ?


Thanks

If you right click on the continuous task and open properties, in the Program/Phase schedule tab you can define the order of execution