Using a list of values from related database in search form

Still cannot understand how is it possible to PROTECT FROM ALL EXCEPT SelectedSuppliers or SuppliersInList that's reffered to BO.

I understand that if I write PROTECT FROM ALL EXCEPT Supplier
it will be accessible for all Suppliers not only for selected. Right?

To make order accessible only to Suppliers that in Order.PriceRequest List I tried to make some queries:
FIND Order WHERE Order.State='Estimation' AND Order.PriceRequest.Supplier=LoggedInSupplier

FIND Order WHERE Order.State='Estimation' AND LoggedInSupplier IN Order.PriceRequest.Supplier

But none of them works. Error:
Attribute path Order.PriceRequest.Supplier is not valid because attribute Supplier has 'multiple allowed' flag on.

Also I used advice from here Calendar View>

and to achieve that I made a rule:
If (TYPE(LoggedInSystemUser)=Supplier AND LoggenInSupplier.PriceRequest<>Order.PriceRequest) Then
PROTECT Order FROM ALL EXCEPT System AND Administrator

But unfortunately awareim doesnt accept it either. Error:
rule '' uses business object 'LoggenInIspolnitel' which has not been found

Could you help me please on this issue?

Error:
rule '' uses business object 'LoggenInSupplier' which has not been found

Very sorry!
The last rule is accepted by AwareIM:
If (TYPE(LoggedInSystemUser)=Supplier AND LoggedInSupplier.PriceRequest<>Order.PriceRequest) Then
PROTECT Order FROM ALL EXCEPT System AND Administrator

But when I enter as any Supplier even that is not in Order.PriceRequest I am able to see the order in query.

This rule helped me 😃 :
FIND PriceRequest WHERE LoggedInSupplier IN PriceRequest.Suplier