Snip..
>
>About sum function, that's aproximately what i'm doing. I sum once and store the values in a custom form array. Then i use the current value and the oldval() to update this array.
>About activerow, i'll try to change with recno(). But otherwyse, ¿is ther a event like rowcolchange in order to not let the user move up or down rows in a grid if we are editing one ?
>Thanks a lot. I've learned something again.
Carlos,
With my poor connection I noticed your reply just seconds ago. Below is a code from one of my grid classes controlling leaving row with arrows :

if !this.freetable
	do case
		case inlist(lastkey(),24,5,18,3,145) ;
			and !empty(dbgetprop(this.recordsource,"Table","RuleExpression")) ;
			and !evaluate(dbgetprop(this.recordsource,"Table","RuleExpression"))
			nodefault
		case lastkey() = 27 ;
			and !empty(dbgetprop(this.recordsource,"Table","RuleExpression")) ;
			and !evaluate(dbgetprop(this.recordsource,"Table","RuleExpression"))
			=tablerevert(.f.)
	endcase
endif

Since I just cut&paste you should play with it some (ie: contains a custom prop ref to freetable). In init related database is opened if not (-if not free-)and freetable is set. It's bypassed with mouse clicks of course. It's an old code and not revised yet. You can extend it for your needs.
Cetin