Excel progression of nrs

Hi there,
I have an excel problem which I hope you guys can help me with

Oke the situation is as follows

I have a colum with random numbers. I have another colum where is shown which number is unique and which is repeating with respect to the previous numbers. Now I want to create a colum where I want 1 to progress with 1 each time a repeating nr comes. When a unique nr comes I want the number to be distracted with 1, hence -1. Furthermore the number can not become smaller than 1. See example

I created the unique repeating formula with:=IF(COUNTIF($B$3:B3,B4),"Repeater", "Unique")

Now I need the formula for the progression

Your help is greatly appreciated!

Random Unique/repeat Progression
37 Unique 1
17 Unique 1
22 Unique 1
9 Unique 1
0 Unique 1
21 Unique 1
37 Repeater 2
33 Unique 1
14 Unique 1
13 Unique 1
5 Unique 1
24 Unique 1
4 Unique 1
17 Repeater 2
31 Unique 1
19 Unique 1
32 Unique 1
22 Repeater 2
14 Repeater 3
9 Repeater 4
10 Unique 3
5 Repeater 4
12 Unique 3

Wow amazing that worked right away. Thanks a lot!

Sorry for cross posting, did not know it was not allowed.
Here is the link for those who are interested

http://www.mrexcel.com/forum/excel-q...ml#post4504534