[R] Interpreting Poisson GLM coefficients into everyday language

[Shawn Morrison]

Is there a readily available function to calculate the effect of 
variables from a poisson GLM on the response variable?

My situation is as follows:

I have developed a poisson GLM model and have obtained the coefficients, 
SEs, etc However, I am somewhat stuck on interpreting a coefficient in 
everyday language.
For example:

Y = dependent variable (count data)
A = independent variable (continuous)
B = independent variable (continuous)


The hypothetical regression equation is:

Y ~ constant + 0.25*A - 0.19*(log(B+1)) [I used natural logs for A]

I want to be able to say that changing B by one unit has a corresponding 
___% decrease in Y.

How do I calculate the % change in Y caused by changes in B? Is there an 
R function, or a bit of code that will do the trick? How do these 
calculations affect the SEs?

Thank you,

***************
Shawn Morrison
Edmonton, Alberta