Here's just a quick and basic one (you can insert code to pick an object and get the name to process one at a time if you like).
Code:
(defun resetXrefs (/ a b xset ent entl)
(cond
((setq xset (ssget "X" '((0 . "INSERT"))))
(setq a 0 b 0)
(repeat (sslength xset)
(setq ent (ssname xset a)
entl (entget ent)
a (1+ a)
)
(cond
((>= (cdr (assoc 70 (tblsearch "BLOCK" (cdr (assoc 2 entl))))) 4)
(setq entl (subst '(10 0.0 0.0 0.0) (assoc 10 entl) entl)
entl (subst (cons 50 0.0) (assoc 50 entl) entl)
)
(and (entmod entl)(setq b (1+ b)))
)
)
)
)
)
b
)