Hi ,
You can always combine the two formulae into one :
=IF(K3>=TIME(1,0,0),SUM(IF($A$3:$A$27=I3,IF($B$3:$B$27=J3,$C$3:$C$27,0),0)),0)
entered as an array formula , using CTRL SHIFT ENTER , into M3 , and copied downwards.
Please note that I have not checked your calculations ; I would urge you to verify them for all possible values of start and end times.
Narayan