Try something like:
VB Code:
' Requred defs...
Private Const LB_FINDSTRING = &H18F
Private Declare Function SendMessage Lib "user32.dll" Alias "SendMessageA" ( _
ByVal hWnd As Long, _
ByVal wMsg As Long, _
ByVal wParam As Long, _
ByRef lParam As Any) As Long
Private Function FindLB(Obj As Object, TextToFind As String) As String
' Set the value as the index...
Obj.ListIndex = SendMessage(Obj.hWnd, LB_FINDSTRING, -1, ByVal TextToFind)
' Set the functiosn return as the ListIndex value.
FindCB = Obj.List(Obj.ListIndex)
End Sub
And then use it like so:
VB Code:
' Declare the return variable.
Dim strTheValue As String
' Set the return value.
' ListBox1 is the object that represents your listbox.
' TextBox1 is the object that represents your textbox.
strTheValue = FindLB(ListBox1, TextBox1.Text)
Label1 = strTheValue
Or, something to that effect 
Cheers,
RyanJ