If I'm understanding this correctly, you cannot open more than one drawing at a time, and your getting dialog box when you want command line capabilities.?.
Check your SDI system variable. If it's set at 1 (one) then you are in Single Document mode, set it to zero.
Also check your FILEDIA system variable. If it's set to zero, you will get command line activity, if it's set to 1 (one) you will get dialog box activity.
I hope this answers your question.