OT: tcl/tk GUI app

[Fred James <fredjame fredjame cnc net>]

All
My apologies for being somewhat off topic (OT), but I don't know where 
else to turn (your pointers in that arena would be appreciated as well).

I am trying to learn some GUI programming and what is readily available 
to me is tck/tk, and I have a (very) little experience with it.

I want to open a dialog to choose a directory, and then put that choice 
into a variable to be used by another action.

So far I can only get the dialog
    set dir [tk_chooseDirectory -initialdir ~ -title "Choose a directory"]
which works fine in and of itself, of course, but I haven't been able to 
use the result for anything as yet.

Any help you may be able to offer would be appreciated.  Thank you
Regards
Fred James