Rota Generator

Hi this may have already been covered somewhere but i cannot find anything.

I am looking at automatically generating a rota based on some parameters.

i have a list of staff and i have a week template with all available shifts that can been filled randomly.

However staff work a different number of shifts each week which is also highlighted.

How can i auto populate this rota to make sure staff are only doing the required number of shifts per week?

I have had a go myself by making a random generator for the week but it just duplicates names too much and i don't know how to set limits on this.

I have attached what i have done so far.

In an ideal world i would like to do this over 2 weeks and give everyone a weekend off that's fair and even.

Thanks in advanced