[ic] require [item-accessories] ?

[Tim Watts <hostmaster@Romans1013.net>]

how do you require [item-accessories] at checkout?

selector looks like this:

             ----
Choose Key: |    |
            | Bb |
            | C  |
            | D  |
            | E  |
            | F# |
            | G  |
             ----

how can I make checkout error if option "" is selected?

tried:
[error name=key std_label="Choose Key: " required=1]

even tried:
[error name="key[calc][item-increment] -1 [/calc]" std_label="Choose Key: "
required=1]

to keep name same as name IC creates in cart, but neither work.

Any suggestions?

Thanks,

Tim