C7 List Box - How do I add addional linking fields?

[emaduddeen]

Hi Everyone,

If my key has 2 columns called INV:category and INV:category_number, how to I
add the 2nd column as a linking field in the list box "Promps" window?

I found "Additional sort fields" but not "Additional link fields" buttons in there.

Thanks,
Emad