last cost

[#1]

hi, this is my facts table

ID	date	type	item	quantity	cost	revenue
1	17/11/09	sell-in	8410	2	230
2	30/11/09	sell-out	8410	1		280
3	30/11/09	sell-out	8410	1		280
4	17/12/09	sell-in	8410	1	220
5	18/12/09	sell-out	8410	1		280

whow can I update the cost in all sell-out row with the last sell-in value? this is for valuate stock with last cost value.

thanks all

[#2]

I think the right practice is:

LOAD *,if(cost,cost,previous(last_cost)) as last_cost resident TB1

but it's not possible in QV