I can't say for sure how it would work for a huge list but maybe something like this will work for you.
VB Code:
  1. Private Sub Form_Load()

  2.     List1.AddItem "Peaches"

  3.     List1.AddItem "Nectarines"

  4.     List1.AddItem "Pears"

  5.     List1.AddItem "Quinces"

  6.     List1.AddItem "Cherries"

  7.     List1.AddItem "Apricots"

  8.     List1.AddItem "Apples"

  9.     List1.AddItem "Plums"

  10.     List1.AddItem "Figs"

  11.     List1.AddItem "Kiwis"

  12.     List1.AddItem "Olives"

  13.     List1.AddItem "Clementine"

  14.     List1.AddItem "Kumquat"

  15.     List1.AddItem "Minneola"

  16.     List1.AddItem "Mandarin"

  17.     List1.AddItem "Orange"

  18.     List1.AddItem "Satsuma"

  19.     List1.AddItem "Tangarine"

  20.     List1.AddItem "Tangelo"

  21.     List1.AddItem "Lemon"

  22.     List1.AddItem "Rough Lemon"

  23.     List1.AddItem "Lime"

  24.     List1.AddItem "Leech Lime"

  25.     List1.AddItem "Grapefruit"

  26.     List1.AddItem "Pummelo"

  27.     List1.AddItem "Sweety"

  28.     List1.AddItem "Ugli"

  29. End Sub

  30.  
  31. Private Sub Text1_Change()

  32. Dim i As Integer

  33.  
  34.     For i = List1.ListCount - 1 To 0 Step -1

  35.         If UCase(Left(List1.List(i), Len(Text1.Text))) <> UCase(Text1.Text) Then

  36.             List1.RemoveItem i

  37.         End If

  38.     Next i

  39. End Sub