attachMovie difficulty. Help, por favor?

I’ve been beating my head against the wall for the last few hours, and my Google fu has turned up nothing.

I have a bunch of empty movie clips on the stage (“Dropdown1” through “Dropdown5”). I’m trying to add menu items to each dropdown dynamically, pulling the info from an XML document. Anyway, I can’t seem to get the menuItem mcs to attach to my Dropdown mcs.

This works fine:
[color=navy]Dropdown1.attachMovie(“menuDropdown_mc”, menuName, 1);[/color]

But if I try and use a variable like this:
[color=navy][‘Dropdown’ + theCategory]attachMovie(“menuDropdown_mc”, menuName, 1);[/color]

the mc gets attached to the root. I tried doing my concatenation elswhere and using a variable name like this:
[color=navy]var DropdownName = ‘Dropdown’ + theCategory;[/color]
[color=navy]DropdownName.attachMovie(“menuDropdown_mc”, menuName, 1);
trace(DropdownName);[/color]

which doesn’t work either (still attaches the mc to the root instead of Dropdown1, although the trace does output the variable “DropdownName” as “Dropdown1”.

Any idea what I’m doing wrong? Thanks!