Stopping and Starting the the SLA clock using another field

Stopping and Starting the the SLA clock using another field

Hi 
New to MSP+ my issue is I need to have a filed where the Request ticket is sent out to an external supplier, when the field is update with a value, this needs to stop the SLA.  When the data value is updated with "Supplier Provided Information" The SLA clock start again. Not sure how this can be done in the Service Level Agreement section in MSP+