Looking for demography software

[K. K. Fung at UMemphis]

I am looking for a software that could plot the future age structure of a human
population given the birth and death rates and the initial age distribution. 
Something like a spreadsheet for demography.  If you know of any such software,
please contact me.  If you have designed one for your own use, I would like to
collaborate with you on a paper about negative population growth.