Lookup in different tab

[Bal_Ocado]

Hi, I am trying to do a sumif from a different file (won't have space in the file i'm currently working on to copy across). It doesn't have to be a sumif, which won't work if the file is not open alongside. My lookup has to have to criteria, the date and the names of sites. For eg.

Sites/Date	01/01/2014	08/01/2014	15/01/2014	22/01/2014
C	1522	1518	2153	5151
H	1536	5151	5123	6269
E	2153	2652	5652	5484
T	2515	5414	6549	9488

<tbody>
</tbody>

So in my file, I want to look up only sites 'C' and 'E' and only for a particular date in my file (which is also weekly and will move with the file). So, I will be looking to fill in something like:

Sites/Date	01/01/2014	08/01/2014	15/01/2014	22/01/2014
C	1522	1518	2153	5151
E	2153	2652	5652	5484

<tbody>
</tbody>

I have been trying to do this in a separate file, but it has been difficult. Any help would be much appreciated.

Thanks