How to create a sequential learning plan

We are in the process of creating learning plans and want learners to have to complete courses in a sequential order.  

1. How do I Iock a course until the learner has completed the preceding course? 
2. Can we assign a timeline to each course (eLearning and ILT) in which the learner has to complete it?  (.e. first week, within 30 days, 90 days, etc.)

Any help is appreciated.  

Cheers!