May not be accurete but atleast should give some idea. Hope this will help.
declare @emptrack table
(
dat date,
tim time,
inout varchar(3)
)
insert into @emptrack values(GETDATE(),'9:30 am','in')
insert into @emptrack values(GETDATE(),'11:00 am','out')
insert into @emptrack values(GETDATE(),'11:15 am','in')
insert into @emptrack values(GETDATE(),'1:00 pm','out')
insert into @emptrack values(GETDATE(),'1:30 pm','in')
insert into @emptrack values(GETDATE(),'3:00 pm','out')
insert into @emptrack values(GETDATE(),'3:10 pm','in')
insert into @emptrack values(GETDATE(),'5:00 pm','out')
insert into @emptrack values(GETDATE(),'5:15 pm','in')
insert into @emptrack values(GETDATE(),'6:30 pm','out')
Select sum(DATEDIFF(mi,a.tim,b.tim)) From
(select row_number() over( order by tim asc) id , tim,dat from @emptrack where inout='in')a
Full Outer Join (select row_number() over( order by tim asc) id , tim,dat from @emptrack where inout='out')b
on a.id=b.id
group by a.dat