What is the time period under Secondary Clause W2, of NEC4, that the Contractor has to notify the Senior Representatives that it disputes a Project Manager’s decision - in this instance the rejection of a Contractor-notified CE? I can see that there is a timeline that starts after notification - one week to substantiate, three weeks for the parties to try to resolve - but none for the period after the PM’s decision to when the Contractor must give notice of dispute.
There is no timescale in which you have to notify a disagreement within to the senior representatives. However - it makes sense to do it as soon as possible as the issue is then more recent/fresh and is going to be less subjective than waiting towards the end of the project. The whole idea of senior representatives is that it is a last chance for the Parties to look at issues that otherwise could go to adjudication. It is not binding though to have to go through senior representatives - the matter can still be taken direct to adjudication, although you might as well at least try senior representatives and see if that can not be avoided by a last mutual agreement.