Assembly or cast unit drawing sheet number
Use match function to find "-" character
match(GetValue("NAME_BASE"),"*-*")
Use of mid function to return only characters after "-"
mid(GetValue("NAME_BASE"),(1+(find(GetValue("NAME_BASE"),"-"))),2)
Combine all above in rule
if (match(GetValue("NAME_BASE"),"*-*"))
then mid(GetValue("NAME_BASE"),(1+(find(GetValue("NAME_BASE"),"-"))),2)
else ""
endif