There's no user's interaction with the panel and i'll set to reload continuously, so, when the last record has the type Start or Pointment , the timer will reset an start the countdown and where has the type Stop or Finish the timer will have the value 00:00:00 till start again.
// store last row operation in a variable LET vLastOperation = Peek('Operation', NoOfRows('TableName')-1,'TableName');
// Create expression based on last row operation IF '$(vLastOperation)'='Start' or '$(vLastOperation)'='Pointment' THEN SET Expression = =interval(variable1-now()); ELSE SET Expression = =interval(0); ENDIF
Try adding Noofrows in a different variable to check: LET vNumRows = NoOfRows('TableName'); LET vLastOperation = Peek('Operation', $(vNumRows )-1,'TableName');
And confirm table rows (in log or Document properties->tables) should be the same as vNumRows, also confirm that the last row has a value in OperationField. 'Operation' should be the field name 'TableName' should be the table name