& PTRACERS_StepFwd
LOGICAL PTRACERS_StepFwd(PTRACERS_num)
IF ( PTRACERS_StepFwd(iTracer) ) THEN
IF ( PTRACERS_StepFwd(iTrc) .AND.
PTRACERS_StepFwd(iTracer) = .TRUE.
PTRACERS_StepFwd(iTracer) = .FALSE.
IF ( PTRACERS_StepFwd(iTr) ) THEN