I think you miss the point of having a backup. Backups should be done on a regular schedule so they will always be as current as needed.
For Time Machine connect the backup drive. Open Time Machine preferences. Select the drive to be used for the backups. The Options butiton will let you exclude drives, folders, and/or files from the backup. Turn Time Machine on using the large slide switch gadget. From there on it's automatic.
If you prefer to have backups occur less often than once per hour then download TimeMachineEditor 3.0.2 and use it to configure your own schedule times.
Be sure you only use the Time Machine backup drive for backups. If you need external storage use a different drive.