SUM OF TIME column CALCULATION NOT WORKING

[paulista]

I am not able to aggregate the time , over the rows.

the aggr i am getting for below is 13.27 but ddefinitely it looks incorrect. the expression used to calculate is 

=IF(IsNull([collateral-valuation-completed]),0,
timestamp(timestamp([collateral-valuation-completed], 'DD/MM/YYYY hh:mm:ss')-timestamp(Min(HDR_TIMESTAMP), 'DD/MM/YYYY hh:mm:ss'),'hh:mm:ss')
)

how can i do SUM of this and average in separate expressions.

[sunny_talwar · Accepted solution]

May be this

=Interval(

Sum(Aggr(If(IsNull([collateral-valuation-completed]), 0,
[collateral-valuation-completed] - Min(HDR_TIMESTAMP)), HDR_CORR_ID))

, 'hh:mm:ss')

[paulista]

thanks sunny for being helpful always