Any webi function like excel's % function?

Hi,

I have a very annoying calculation problem in Web Intelligence.

Here is the situation;

I have the revenue according to calmonth for last twelve months and i divide revenue for the previous one, in turn. So i can find all the revenue changes in months.

Then data's look like ;

calmonth revenue changes start with 100 then formula

2010.06 6.963.912 100,00

2010.07 6.169.853 -11,40248074 88,60

2010.08 5.735.882 -7,033731445 82,37

2010.09 6.574.229 14,61584189 94,40

2010.10 7.134.662 8,524688675 102,45

2010.11 7.718.674 8,185557214 110,84

2010.12 7.052.929 -8,625119079 101,28

2011.01 7.431.386 5,365948224 106,71

2011.02 8.171.785 9,963135475 117,34

2011.03 7.751.925 -5,137913352 111,32

2011.04 8.199.208 5,769956621 117,74

2011.05 9.168.454 11,82121518 131,66

I can make the start with 100 in excel but i could not make it in webi.

Changes: revenue/previous(revenue)*100-100 // can do it in webi easily

Start with 100 formula in excel: 100*(1+-11,40248074) // can not do it in webi!!

Is there any function or solution to help me?