How to adjust or modify named boundary?

Hi Everyone,

I just finished cutting and annotating my striping sheets with the named boundary tool. One particular sheet cuts into 1/8 of a turn lane so I want to modify the named boundary on that one sheet or the next sheet so that only either sheet shows the complete turn lane. 

I was not able to do the adjustment on the sheet model or drawing model. Is there a way to do it or I'll have to restart in the design model where I originally started? Recreate the sheet from scratch. I don't want to re-annotate eveything.

Thanks!