Option Group to filter form

I'm confused?
1. You can't really filter the form records, if the combobox values will remain the same...
(The values in the combobox should reflect the values displayed in the form)
Meaning, ... your filter might exclude values displayed in the combobox...
For example:
If you filter the form for (lets say) USA, ....then you only want USA values in the combobox)
In other words, ...if you filter the form for a certain value, ...you must also provide a way to filter the combobox for that same value.

2. Your design is a bit confusing, ...I am not understanding the relationship between CountingUnitID and the option group values.
for example, ...what CountingUnitID  represents New, Existing and All.
In your table, you only have CoutingUnitID values of One and Null
But the source for the combobox is 1 through 11
CountingUnitID      CountingUnitType
1      Each
2      Gallon
3      Bundle
4      Package
5      Box
6      Capsule
7      Bag
8      Pound
9      Case
10      Quart
11      Pint

How do these values relate to: New, Existing and All.

...Or am I missing something?

Hi,
Sorry, I should have provided more detail.  The records will be appended then updated by query from Excel when new purchasing histories are available.  When a new item is imported, there is no data in the counting unit field, so I'm using that field to identify new records for the end user (who then has to add the counting unit, locations, etc.).  The option group will provide a quick way to access these.  Your comment about the combo box filter is just what I'm trying to do,  Thanks!

Although not exactly what you have, ...I believe this represents what you are after.

Thanks