Display three picklist dependent on each other (while editing one pick list other two should get ref

Hi, 
Please consider this data model, 
Account –> Opportunity –> OpportunityLineItems 

I have account as my master model. so according to my understanding I can pull only account field in layout. 

now, the requirement is once I have to display related opportunities in picklist and once this picklist selection is changed, I have to render another picklist which will contains OpportunityLineItems of selected opportunity. 

I am able to achive first part to show all opportunities related to that account in picklist through custom render, but not sure how can I render another picklist which contains only those opportunityLineItmes related to selected opportunity.

we are new to skuid and any code sample will be very helpful.

Thanks in advance.