Exponent calculation

Hi all, 

I have a column decimal with varying powers say 0,10,18,28 etc. Another column amount, which contains different values. My task is to create a new column which does the following function,

New column = if decimal <> 0 then (0.05*amount)/10^decimal 
else (0.05*amount)/10

I can't figure out how to do this. Creating a measure with exp option provides a feature to use an exponential function with a specific number only. I would like to generate exponential value for a column and perform the above operation. 

Can somebody help me in pointing out in the right direction?

Thanks,

Indhu.