For now, what you can do is this...
Open your CamBam drawing.
Start another instance of CamBam and into this load your revised DXF file.
Copy the changed parts of your DXF to the clipboard then paste them into your CamBam drawing. You may want to delete the changed parts from your CamBam drawing first.
You then need to relink your machining operations with your changed drawing objects. There are a few ways to do this.
Right click the machining operation then select 'Select drawing objects'
Change the IDs in the Primitive Id list property of the machining op.
Select the new drawing objects then drag them in the drawing tree, onto the machining operation icon.
I tend to use the last method the most.
I hope this helps.