continuously evaluated prompts/environmental variables

[Edward Peschko]

All,

I was wondering if there was a way to make an environmental variable
be evaluated each time it was accessed. In other words, with:

export PS1="`whoami`@`hostname`"

This works for the first time that the prompt is evaluated, what I
would like to have is a prompt to be continuously evaluated, so that
if whoami or hostname changes, the prompt changes along with it.

Is there a way to have the prompt - or any other environmental
variable - change in this way, based off external command?

Thanks much,

Ed