Check If ID Is New Then Sum Per Category

I have 4 columns:

id (A), number (B), category (C) and month (D)

I think this could be done using VBA or formula's,
I understand how to SUM up based on criteria, but I
haven't a clue where to start to see if something was
present/ not present in the previous month and category and vice versa

If I decide a month to look at in E1, say February.. then i need
to calculate 4 things:

1) was an id in February and not in January (for this category) if so then sum up (B) per category (C) for February

2) was an id in January and not in February (for this category) if so then sum up (B) per category (C) for January

3)was an id in February and not in January (not in any cateogry in jan) if so then sum up (B) per category (C) for February

4)was an id in January and not in February (not in any category in feb) if so then sum up (B) per category (C) for January

I need to do this for each category (C)

My data would be something like this (I cant download addon from this PC, i have it at home)

id____number____category____month
1_____10_________A___________january
2_____20_________A___________january
3_____30_________B___________january
4_____40_________B___________january
1_____50_________A___________february
2_____60_________A___________february
3_____70_________A___________february
5_____80_________A___________february

so if I chose to put February in E1,

I would need the results something like follows:

category__new to category__left category__n__left totally
A___________(70+80)__________none____________(80)________none
B___________none____________(30+40)__________none________(40)