In your cbohmoi combo, make sure to include BOTH fields from the table in your RowSource. You can hide the second one (the one showing the County) by setting ColumnCount=2 and ColumnWidths=0;1. The RowSource for your cbonomoi combo would be ONLY the County field from your table.
Now, in the AfterUpdate event of cbohmoi:
Sub cbodhmoi_AfterUpdate
Me.cbonomoi = Me.cbohmoi.Columns(1)
End Sub
Note that Columns is zero-based, so the code above refers to the 2nd column in cbohmoi.
<I also dont want the value in the combo box to be inserted to the table tblnomoi when a key is pressed from the keyboard>
Then don't "bind" that combo to anything - set the ControlSource to an empty string. If you do that, you'll also have to include code such as shown above in the Form's Current event, which fires every time the user changes to a different record in that form.