Filling a listbox with unique entries in a row based on certain criteria

Hey everyone,

I'm still fairly new to VBA and am trying to create a - by my standards - complicated sheet with control elements. The idea is that the user chooses two data properties in two drop down menus. Then, the listbox is supposed to fill with unique values that are based, or filtered if you will, depending on those properties.

For the filling with unique entries I am currently using a collection code that I borrowed from another forum post. It looks like this:

'Fills the left textbox with all available CG3s and sorts them alphabetically
Dim myHeight As Integer
Dim myWidth As Integer
Dim myRange As Range
Application.ScreenUpdating = False

'Finds the last cell with data in a given column
Call LastRow(5)
lstCG3base.Clear
myHeight = lstCG3select.Height
myWidth = lstCG3select.Width

With Worksheets("Raw_Data")
Me.lstCG3base.List = GetUniqueItems(.Range(.Cells(5, 8), .Cells(iRowNum - 1, 8)))
End With
Call SortListBox(Worksheets("CG3").lstCG3base)
With lstCG3base
    .Width = myWidth
    .IntegralHeight = False
    .Left = 27.75
    .Top = 189
    .Height = myHeight
    .Width = myWidth
    .IntegralHeight = True
    .Left = 27.75
    .Top = 189
    .Height = myHeight
    .Width = myWidth
End With

Now what it's supposed to do is to look within the row of a cell whether the properties selected in the dropdown menu are met, and either add or don't add the unique entry to the listbox depending on that.

The cool thing about the above code is that it's very fast, as the list I'm dealing with is quite big. Is there any way to accomplish this, or do I need to rethink the entire filling code?

Thank you very much in advance

PS: I meant entries in a COLUMN in the title, not a row.