retrieve values

I have a table in which there are 3 fields:

Item No., REfType and RefNo.

Reftype is an option field with Rel.Production Orders and Released Sales Orders as items.

RefNo. is lookup field.

when we select Rel. Production Orders, only the released prod. orders of the selected item no. should be dispalyed.

how?

Is there any form involved, if yes then you can filter (Press F7) in the Reftype and select the option and press OK.