If work stoppage applies to a few activities then copy the activities calendars to new calendars, apply the exception to the new calendars and assign to these activities and affected lags.

• Take for example in a job with several buildings some underground problem was discovered on one building and a directive mandate stoppage only to this activity. Then the above procedure might do it.
• Unforeseen subsurface conditions: A problem beneath us (INTERNATIONAL BAR ASSOCIATION) Over the last several decades, a number of contracts have sought to share the risk of encountering unforeseen subsurface conditions. The principal mechanism for doing this is to compensate the contractor for subsurface conditions that are not foreseeable. Clause 4.12 of the FIDIC Red Book 1999 edition, for example, entitles a contractor to claim an extension of time for delay to completion and payment of cost for adverse physical conditions that were not reasonably foreseeable by an experienced contractor, subject to giving appropriately timed notices and meeting other criteria. However, a raft of English law cases show that it remains difficult for contractors to satisfy the necessary requirements, particularly the test of foreseeability. Be reminded contract clauses can shift responsibility.
• I recall a case in which this happened but a complete redesign with new activities was required.

Anyway, until a new directive or change order mandates something else you have no option than delay what is still under the contract.

• If you do not know the finish date of the stoppage then adjust it for as long as the work stoppage continues active as you shall keep a contemporaneous schedule for it to represent current plan.
• Put it on record the delay even if not critical might be disrrupting your activities and resource planning and it comes at a cost.