I'm not sure I follow what you're doing, and definitely don't follow when it's being done.
Using the _Change() event will fire the FillCombobox procedure every time any character is typed into the combo box.
I'd think you would want the drop downs to populate before entering anything.
Perhaps using the _GotFocus event instead of _Change.
Code:
Private Sub ComboBox1_GotFocus()
Call FillCombobox("List", "A", Me.ComboBox1)
End Sub
and like this for the FillCombobox procedure
Code:
Sub FillCombobox(WSName As String, ColLtr As String, CBox As ComboBox)
Dim LastRow As Long
Set ws = ActiveWorkbook.Worksheets("List")
With ws
LastRow = .Cells(.Rows.Count, ColLtr).End(xlUp).Row
CBox.List = .Range(ColLtr & "3:" & ColLtr & LastRow).Value
End With
End Sub