How do I do Sub Object Custom Validation mvc3

[tanie1Spomaopelay]

I have an object (header) that has a list of sub-ojects (details) that I want to do custom validation on prior to accepting data. I've tried ModelState.IsValid and TryValidateModel, but it doesn't seem to fire the Validate method on the sub-objects (only the header object).So on submission I see the validation fire for the header, but not the sub-ojects. Then if I do a TryValidateModel I again see (breakpoint) the validation method get called on the header, but not on the sub-objects.The annotated validation (must be number, etc...) seems to be working on the sub-objects, just not the custom logic added via the IValidatableObject interface. Any help would be greatly appreciated.