Workflow to change Detected on Date to current date on the new Defect created on COPY AND PASTE of existing Defect.

Not finding much information on COPY and PASTE of a Defect in Desktop Client workflow commands/syntax.
I have looked at 'Sub Defects_Bug_New' workflow and tried adding something to this effect..

Bug_Fields("BG_DETECTION_DATE").Value=Cstr(Now())

but this is not changing anything ... the defect detection date is exact copy of the source...

Would like to automate the change on paste so the date is the data of the copy event.

Any point in the right direction is appreciated!