Sum values based on multiple unique criteria

[Bobmufc08]

Hi chaps,
In worksheet 1 I have the below data. In worksheet 2 in cell A1 I have the date 01/01/2017.
Using the EOMONTH function I am able to refer to the date in A1 to sum the whole of January 2017 in my data.

I need to sum column E below, however I only want to sum column E once for every occasion where the contents of columns A C & D are duplicated.
For example, 03/01/2017 below should total 9 rather than 18 because A C & D are all the same. Where as 05/01/2017 should total 14 because even though column A is the same, C & D are different.

In addition to this, where column B is blank I don't want it summed at all, regardless of the contents of columns A C & D.

I've tried adapting various sum/frequency/sumproduct formulas with little progress so far.
Is my goal here actually achievable without the use of macros? Any help much appreciated
Thanks

A	B	C	D	E
01/01/2017	Customer A	Teacher 1	Course A	9
01/01/2017	Customer B	Teacher 1	Course A	9
01/01/2017	Customer C	Teacher 1	Course A	9
03/01/2017	Customer D	Teacher 2	Course A	9
03/01/2017	Customer E	Teacher 2	Course A	9
05/01/2017	Customer F	Teacher 3	Course B	5
05/01/2017	Customer G	Teacher 4	Course A	9
08/01/2017		Teacher 2	Course C	10
09/01/2017	Customer H	Teacher 1	Course C	10

<tbody>
</tbody>

 

[boochang]

You need to create a "helper" column. Paste this in column F or something. =IF(A3=A2,"",SUM(E2:E3))

 

[Bobmufc08]

You need to create a "helper" column. Paste this in column F or something. =IF(A3=A2,"",SUM(E2:E3))

Cheers boochang, doesn't this rely on the data set being sorted in date order though? It also doesn't appear to consider the contents of columns C & D.