Change calculation period for amortization of other flows

Hi all,

My company has a credit facility set up in FSCM - TRM.  Recently, this credit was extended by one year.  The users can change the End Date in the Structure tab of the deal, to add one year. They also want to extend the period over which the Other Flows are amortized by one year.  However, the end date for the calculation of amortization of other flows is greyed out and cannot be changed.  How can I make the required change?

Thanks,

Dawn