Once you enter into an IVA then you cannot pay off any of your creditors yourself. A dividend will be set and your payments will be geared to that.
If you get any extra money during the term then this will go towards all of your creditors, not just one.
Sharing from experiences of dealing with debt
The greatness of a man is not in how much wealth he acquires, but in his integrity and his ability to affect those around him positively.
Bob Marley. http://kallis3.blogs.iva.co.uk