Manual start date with dependency

Hi.

Im tyring to implement Task B only being able to commence after the completion of Task A while being able to maintain its dependency on Task A and filling in a manual start date for Task B.

So for example

Task A completed January 1

Task B Can start anytime after January 1

Task B Start date can be entered manually

Task B remains dependent on completion of Task A

My problem is if I enter a manual start date for Task B, its dependency on Task A is deleted.

Thanks for your help.

Jason