Trigger PO auto fill button from script

Hello, I have a workflow action script (Suitescript 1) that makes changes to new PO’s created from the Purchase->Order Items page.

This works fine but for one thing: since we use Suitetax tax details need to be filled. I am hestitant to do this in the script, calculating taxes is very vulnarable to small differences in rounding.

In edit mode on a new PO there is the auto fill button. This pretty much runs the tax details calculations. I would like to trigger this button in my script, so all the tax details are filled correctly.

How can I invoke a Netsuite standard button like this one from a script? All help greatly appreciated, it’s something we really need to get working!