This has been passed to me as a matter of urgency to help you.
An undertaking as you know I am sure is a promise to the court. You can amend an undertaking but only by taking the matter back to the court. If you were to breach the undertaking it is a contempt and you could go to prison. You would need to take the matter back to court and seek the permission of the court to amend it. This is not however uncommon, particularly if your wife supports the change.
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