Q - Can we turn off the ability for users to enter an order for a customer on Credit Hold?

A - Yes, you can. Please go to Elliott Main Menu -> Util_Setup -> Global Setup -> Cop-Ctl -> Credit Check & Release. For the following field, set the value to "N" and save it: 

3. Allow Users To Enter Orders For Customers On Credit Hold? 

That should do it. See sample screen below.