I'm trying to do a sum product with the attached data:

A B C
List of ID numbers Date Time (hh:mm:ss)
Mobile 11 18/03/2007 00:00:30
Mobile 11 18/03/2007 00:01:25
Mobile 11 19/03/2007 00:01:00
Mobile 25 18/03/2007 00:02:01

So I want to sum the time in hh:mm:ss for ID 11 for 18/03/2007.

Looks like its =Sumproduct(--(a2:a5="Mobile 11"),--(b2:b5="18/03/2007"),c2:c5)
but I keep getting errors e.g value or name??

Any suggestions please?