Forms :: Limit Filter To Current Row Of Continuous Form

I've built a basic inventory management system that allows a business to add products and the ingredients (and labour etc.) that go into them so they can work out costs and profit.We've run into a bit of a usability problem in the sense that they have 700 different ingredients and so adding them to products has become a little unwieldy as the lists in the comboboxs are massive.

What they've asked me to do is to add a filter combobox to the Ingredients subform of their New Product page that allows them to constrain the Ingredients by type, to make the lists more manageable. So if you imagine they are entering a record for a new cake and need to add Eggs as an ingredient they could either...

a) Scroll through the list of 700 ingredients as they do currently and find "Size 3 chicken egg".

...or...

b) Use a combobox on the ingredient row to pick "Eggs" which would in turn filter the ingredients combobox on that row from 700 ingredients down to a handful e.g."Size 1 chicken egg", "Size 2 chicken egg", "Size 3 chicken egg", "Size 1 duck egg" etc.

the filter combobox applies to all rows in the subform! Is there a clever way of telling the Filter to only apply itself to the current row of the continuous form?My code is...

Code:
Private Sub FilterRMs()
Dim mySql As String
If Me.RMTypeFilter.Column(1) = "999" Then
Me.FilterOn = False

code]....