How to adjust start date on secondary assignments

We have an employee that has multiple assignments, one of the secondary assignments was entered in with an incorrect start date.

Is there a way to adjust the assignment to be earlier than the current start date? Can this be accomplished through the UI or does it need to be done using an HDL load?

In this case, the date needs to be adjusted to a few days earlier. Note: Several payrolls have ran since that time. Will that complicate the adjustment to the start date if we are making it earlier than what is currently in the system?

Thank you!