CS3 Extended Plugin Options?

I'm trying to write a 3D file format plugin for PS CS3 Extended, and I would

like to give the user a way to change the import options.



Question is, where are they?



I don't see any Options... button in the Open File dialog, so

how do you access the import options for a 3D plugin?



Can someone tell me what actions invoke these cases:

- formatSelectorOptionsPrepare

- formatSelectorOptionsStart

- formatSelectorOptionsContinue

- formatSelectorOptionsFinish