Field Data dependant on First Field input

[Paul_birm]

hi hope you can help with this folks...
i have a form which opens a subform.
on the 1st form, the user puts in a Part Number
when the subform opens, the PartNumber is prepopulated
but a field next to the part number needs to go away and look at a list of BOM items and populate the child parts for the number of Child Parts on the BOM this is NOT doing this and i just dont know were to start with the VBA coding.

the first form looks something like this (no gui!)

Order No Part No
[_12345_] [ABC123__]

{open subform button}

the subform looks like this:-

Part No BOMChild BOMQty Added?
[ABC123__] [ *** ] [__] [_]
[ABC123__] [ *** ] [__] [_]
[ABC123__] [ *** ] [__] [_]
[ABC123__] [ *** ] [__] [_]

!note1! BomQty and Added will be entered by the user
!note2! BOMChild SHOULD find the correct parts that have 'ABC123' as their BOMParent part

Hope you can help!!!

thanks in advance

P@ul