Tkinter StringVar mystery

[Bob Greschke]

First off I have this class (thanks to whoever came up with this way back 
when):

######################
# BEGIN: class Command
# LIB:Command():2006.110
#    Pass arguments to functions from button presses and menu selections,
#    bind's.  Nice!
#    In your declaration:
#        ...command = Command(func, args,...)
class Command:
    def __init__(self, func, *args, **kw):
        self.func = func
        self.args = args
        self.kw = kw
    def __call__(self, *args, **kw):
        args = self.args+args
        kw.update(self.kw)
        apply(self.func, args, kw)
# END: class Command


Then in the setup part of an entry form I have:

# CHBCBarcodeLastVar is the variable for an Entry() field
Button(SubFrame, text = "Print Barcode", \
        command = Command(test, "other", CHBCBarcodeLastVar.get(), \
        "CHBC")).pack(side = LEFT)


Then this is a/the test function:

def test(What, BC, Where, e = None):
# Does print the correct value
    print CHBCBarcodeLastVar.get()
# Does change the field on the form
    CHBCBarcodeLastVar.set("55555")
# BC is ""
    print ":"+What+":", ":"+BC+":", ":"+Where+":"
    return

Everything works as it should, except when the Button is clicked BC is an 
empty str in test().  How come?  (I really have NO clue how that Command 
class works, but I use it like crazy.  Is it the problem?)

Thanks!

Bob