diff --git a/examples/PS4000A_ID_Block_Adv_Trigger_PWQ_Example.m b/examples/PS4000A_ID_Block_Adv_Trigger_PWQ_Example.m
index 3a59401..79411b1 100644
--- a/examples/PS4000A_ID_Block_Adv_Trigger_PWQ_Example.m
+++ b/examples/PS4000A_ID_Block_Adv_Trigger_PWQ_Example.m
@@ -322,8 +322,9 @@
 ylim(axes1, [(-1 * chAInputRange) chAInputRange]);
 
 % Plot the trigger position
+numPreTriggerSamples = get(ps4000aDeviceObj, 'numPreTriggerSamples');
 hold(axes1, 'on');
-triggerPosn = (numSamples)/2 + 1;
+triggerPosn = numPreTriggerSamples + 1;
 plot(axes1, timeMs(triggerPosn), chA(triggerPosn), 'rx');
 
 title(axes1, 'Block Data Acquisition');