Sum for Value Column with two dimension rows, in the first dimension row

[tpb04238]

Hello I have a pivot table created that lists the 1st Line Tickets and their associated 2nd Line tickets. I have created a measure that adds up the time the second line tickets are open factoring in overlap and gaps. I want to have the first row in that column (The 1st Line Ticket) be the time the 1st line ticket was open minus the sum of all the below 2nd line ticket rows. This way we can see how much time the 1st line ticket was open without any open 2nd lien ticket. I cannot figure out how to total these rows up. for the 2nd line ticket rows I have the following expression

if(rowno()=1 , RelActTICKET_ACTUALFINISH-RelActTICKET_ACTUALSTART,
if(rowno()<>0 and Rowno() <>1 and RelActTICKET_ACTUALSTART<above(RelActTICKET_ACTUALFINISH) , RelActTICKET_ACTUALFINISH-above(RelActTICKET_ACTUALFINISH),
if(rowno()<>0 and Rowno() <>1 and RelActTICKET_ACTUALSTART>above(RelActTICKET_ACTUALFINISH), RelActTICKET_ACTUALFINISH-RelActTICKET_ACTUALSTART,
)))

I need what is currently showing as '0' in the 2nd Line OT Check to be the sum of the below rows.