{THEME_SELECT_LIST} in theme.php?

[Crrash]

for the main menu i added a table (in the theme.php) looking like this

__________________________________________
|____________________A____________________|
|__B__|______________C_______________|__D__|

in cell "A" cell "C" and Cell "D" i put the normal main menu buttons

cell "B" has a background which looks like the buttons, but without the inscription
in Cell "B" i want to put the theme select dropdown list

all the buttons (including the background of cell "B") have perfect transitions to the buttons to the left and right, so there shouldnt be any borders between the background of cell "B" and the first button of cell "C"

the problem is, that {THEME_SELECT_LIST} wont work in theme.php what can i do to insert the dropdown menu at that place?