Lookup questions cross worksheets

[John S]

I am using Excel 2007 and I have two worksheets in the same workbook. Each
month I will be comparing data from the current months data to the prior
months data.

The worksheets look like below


Worksheet - Prior Month


Acct No. Type
1 a
2 d
3 a
3 g
4 d
5 g
5 e
6 f
8 d


Worksheet - Current Month

Acct No. Type
1 a
2 e
3 a
3 d
4 d
5 g
5 e
6 f
8 d
9 e
9 d
10 g
11 a
11 e
12 d
13 f


Things to note:

1. An account may have more then 1 type attached to it
2. New accounts will be added each month
3. The type for each account may change each month

I need a way to identify all the following:
a. All accounts that are currently have a type of "d" and were type"d" last
month
b. All accounts that have a type of "d" in current month and were not type
"d" last month
c. All accounts that are not type "d" in the current month but were type
"d" in the prior month. ( This is the part I am stuck on)

I would like this to be one excel worksheet that provides all this data.

Any help is appreciated.

Thanks
they were type "d" last month or if this is the first month they are type "d"