--- a/dwm.c	2012-12-06 20:11:18.000000000 -0600
+++ b/dwm.c	2012-12-06 20:11:18.000000000 -0600
@@ -152,6 +152,7 @@
 	unsigned int tags;
 	Bool isfloating;
 	int monitor;
+	void (*callback)(Client *c);
 } Rule;
 
 /* function declarations */
@@ -316,6 +317,8 @@
 			for(m = mons; m && m->num != r->monitor; m = m->next);
 			if(m)
 				c->mon = m;
+			if(r->callback)
+				(*r->callback)(c);
 		}
 	}
 	if(ch.res_class)