Summing based on several conditions

I have used various formulas but cannot get it right its annoying me now;

Tried:

=SUM(IF($D$2:$D$202=$T$10,Task_Timings!$B$10+SUM(IF($D$2:$D$202=$T$10,IF($H$2:$H$202="Yes",Task_Timings!$C$10)))))

Tried:

=SUM(IF($D$2:$D$202=$T$10,Task_Timings!$B$10),SUM(IF($H$2:$H$202="Yes",Task_Timings!$C$10)))

Seems to just calculate random figures and sum everything up wrongly.

What it should do is;

IF D2:D202 contains whatevers in T10 AND H2:H202 contains the word "Yes" it will then add together Task_Timings B10 and C10. But IF H2:H202 contains nothing then it should just give the Task_Timing B10 value.

Thanks,