How To: Replicate the "Use existing PST file (if exists)" seen in GUI when using powershell

Problem:

When exporting from Office 365 Exchange to PST files using powershell, you want to use the option to replicate the "Use existing PST file(if exists)" option which is found in the GUI. Is there a switch or perhaps a syntax which can achieve this?

Resolution:

You can use the -UseExistingPST switch

eg Export-MessageOps.ToPST -UseExistingPST