optimalize search with textbox

Hi,
pls. how can i optimalize thic code, that it works faster, better?
and how to change it that it will return only unuique value to column C?

is here possibility how to make faster to search in huge table?
i want to use it for search in big table...i have defined ranges in 2 sheets, but it take a long time ..
what can i do, that will works faster?

e.g. i have this code (but i will define more as one sheet)
and it take a long time to searching only in a few cells..what will do with 7000 row ?

Private Sub TextBox1_KeyDown(ByVal KeyCode As MSForms.ReturnInteger, ByVal Shift As Integer)
If KeyCode = 13 Then
Dim i As Long, j As String
Range("C:C").ClearContents
j = UCase(TextBox1.Value)

 If TextBox1.Value = "" Then Exit Sub
For i = 1 To Range("A65536").End(xlUp).Row
    If InStr(1, UCase(Cells(i, 1).Value), j) > 0 Then
        Range("C65536").End(xlUp).Offset(1, 0).Value = Cells(i, 1).Value
    End If
Next i
        Me.TextBox1 = vbNullString
    End If
End Sub

thx to all