Automatically Fill A Table From Data In Other Tables

I have 3 tables:

Student Info:
Student ID (Primary Key)
Name etc.

Assignment Info:
Assignment ID (Primary Key)
Assignment Number
Criteria Number

Grades:
ID (Primary Key)
Student ID - Linked to [Student ID]
Assignment ID
Criteria Number
Grade

What I would like to do is be able to link the tables in such a way that for each student entered in the Student Info table, entries are automatically entered into the grades table for each assignment criteria.

For example:
Assignment 1 has criteria 1.1, 6.3, 7.2, Assignment 2 has 4.2, 3.3

When John Smith is entered in student info, the grades table is automatically updated with 5 new entries in the form:

John Smith - 1 - 1.1 - Enter Grade
John Smith - 1 - 6.3 - Enter Grade
John Smith - 1 - 7.2 - Enter Grade
John Smith - 2 - 4.2 - Enter Grade
John Smith - 2 - 3.3 - Enter Grade

That way I can have a form that automatically shows the possible criteria for each assignment on the sub form for each available student without having to type it in each time.

Your help would be wonderful