Help required with changing SLA due dates

RT 3.8.6
SLA 0.03

Hello All

I need some help I have SLA working with both Response and Resolve but need help with a scenario

We set a hard date for resolution

What I need to be able to do is the following

If a ticket is updated with just an update for the client the clock continues to run, if however the ticket is sent back to the client requesting more information or evidence the clock is stopped and restarted with a new due date calculated from the time taken for them to respond is this possible.

The client has a username on RT, would it help to re-assign the ticket to the user, each client has its own Queue and the client can only see that queue and tickets

We do not allow clients to see comments in tickets

Thanks for any help

Regards Simon