draw chart for range by condition

[GMara]

Hi all,

I'm trying to draw chart for the range which members meet some criteria.

Date letter count
1-Jan-08 a 10
2-Jan-08 a 5
3-Jan-08 a 4
4-Jan-08 a 8
5-Jan-08 a 3
6-Jan-08 b 6
7-Jan-08 b 9
8-Jan-08 c 7
9-Jan-08 c 4
10-Jan-08 c 10

I want to draw 3 separate charts for the counts on each date for letters "a", "b" and "c" (see attached .xls file).

TIA
Best,
GMara.