Make Dependent Drop Box Searchable

I may be shooting for the mirror here, but some of my dependent drop boxes have 100+ options in it, so it would be nice to be able to have a search function when using the form's drop down menu without the user having to click on the drop down menu and then start typing - its very counterintuitive to the people who have tested my sheet so far. All of the searchable drop box solutions I found don't use dependent lists, and I can't find a way to make them work with the way I have it set up.

Is there a VBA solution to make the employee drop box searchable with the way I have my dependent drop lists set up? Do I need to start over and try to come up with a pure VBA solution? What would be best at this point?

Searchable Box.JPG

Since I can't upload the sheet (I keep getting an upload failed notice), here is the code:

Private Sub cboEmp_DropButtonClick()

Select Case txtDIR.Value
    Case Is = "OOC"
        cboEmp.RowSource = "OOC"
    Case Is = "RM"
        cboEmp.RowSource = "RM"
    Case Is = "GM"
        cboEmp.RowSource = "GM"

End Select

End Sub

I am playing with something like this from StackOverflow, but I seem to be misapplying it:

Public Sub FilterComboBox1(strFilter As String)

    If Sheet1.ComboBox1.ListIndex > -1 Then

    Else
        Sheet1.ComboBox1.Clear
        For Each strchoice In colChoices
            If InStr(1, strchoice, strFilter) <> 0 Then
                Sheet1.ComboBox1.AddItem strchoice
            End If
        Next
    End If

End Sub

I also found some autocomplete ones, but I am not sure where to put them with the Case/Select functions:

comboBox1.DropDownStyle = System.Windows.Forms.ComboBoxStyle.DropDown;
comboBox1.AutoCompleteMode = AutoCompleteMode.SuggestAppend;
comboBox1.AutoCompleteSource = AutoCompleteSource.ListItems;