Example orchestration pause rule based on SO line EFF being NULL / not NULL

Hi,

Can anybody provide the exact Pause and Release rule for a custom pause process based on a SO Line Flexfield (EFF) being populated?

The business requirement is to pause the orchestration process after the shipment is confirmed if a line level EFF is NULL. Once the EFF is populated (with any value), the pause should be released and it moves to 'Awaiting Billing'.

I cannot seem to find any examples which are exactly the same as this. Other examples are based on the EFF having a specific value such as '9999'. However, this is simply based on EFF being NULL or NOT NULL.