autofill textbox??

Private Sub update_store()
Dim ws As Worksheet
Dim store_name() As String
Set ws = Worksheets("sheet1")
 
' gets last populated row in column 4 
irow = ws.Cells(Rows.Count, 4).End(xlUp).Row + 1
 
'initializes array length
fcount = 0
 
'defines array
ReDim Preserve store_name(0 To 1) 
store_name(0) = ""
 
'loops through all rows to search for unique values
For x = 2 To irow 
    y = 0
 
' loops through list of unique values stored in array
    Do While y <= fcount 
 
'tests to see of value already stored
        If ws.Cells(x, 4) <> store_name(y) Then 
 
'store value only if checked all saved values
            If y = fcount Then 
 
' increases array size
                ReDim Preserve store_name(0 To fcount + 1) 
 
' stores new value to array
                store_name(fcount) = ws.Cells(x, 4) 
 
' causes loop for exit
                y = y + 2
 
'increase count of array size 
                fcount = fcount + 1
            End If
 
'exits loop if value present
        Else: Exit Do
 
 
        End If
        y = y + 1
     Loop
Next x
 
' clears current values of combobox
me.store.clear 
 
' writes new values to combobox 
For z = 0 To fcount 
With Me.store
        .AddItem store_name(z)
End With
Next z
End Sub