Tab command in SAP ABAP

How does the tab command work? It wasn't working the way I expected it to so I create a small script for screen 7200 (transaction IW21,
Plant Maintenance Create Notification)

So, the only thing in my file sapliqs0.e7200.txt is this:

tab P[SetStatus] P[StatusDetail]

I would expect that if the set status pushbutton was highlighted and I hit the tab key, the cursor would move to the left and highlight the status detail pushbutton, yet it doesn't. Also, I understand that the script only runs through once. Then how does the tab command work if the user goes back to the field more than once while entering data. Does it have to in an input script?

I checked the synactive site and it shows the syntax the same as my command. I also tried 'tab [SetStatus] [StatusDetail]'. What am I missing?

Thanks.