Proper defination of usp15

In the following formula,
usp=Highest High in RSI overbrought zone in lower time frame (ie, rsiovb )
usp15=Highest High in RSI overbrought zone in higher time frame,ie 15 Minute time frame
usp = ValueWhen( rsiovs, HighestSince( Ref(rsiovb,0), high ) );
usp15= ValueWhen( rsiovs15, HighestSince( Ref(rsiovb15,0), high ) );
(rsiovs15 AND rsiovb15 is obtained by using TimeFrameExpand function in i Minute chart )
defination of usp AND lsp is working fine.but usp15 AND lsp15 is not working properly.
if you kindly provide the proper defination of usp15
I will be obliged .