I have 3 combo boxes and 1 grid. I want to be able to use the first combobox which will filter what is shown in the 2nd combo box, and the 3rd combobox is based on the first 2 combo boxes.

If the RowSourceType of your dependent combos is 3-SQL Statement, all you need to do is put code like this into the Valid method of the "Master" combo box:

WITH Thisform
  .DependentCombo2.Requery()
  .DependentCombo2.ListIndex = 1
  .DependentCombo3.Requery()
  .DependentCombo3.ListIndex = 1
ENDWITH

And in the Valid method of the second combo box, you would use this:

WITH Thisform
  .DependentCombo3.Requery()
  .DependentCombo3.ListIndex = 1
ENDWITH