[pstricks] accessing pstricks dimensions

[John Frampton]

In need to access pstricks internal dimensions, `armA' or 
`nodesep' for example.  Looking at the pstricks code led me to try:

    \catcode`@=11
    \pssetlength\dimtemp\psset at nodesep
    \catcode`@=12

as a way to get the nodesep dimension into the dimension register 
\dimtemp.

But this doesn't work, for reasons that I do not grasp.

Could anyone help me out with this?

Thanks,
John Frampton