How to autocomplete textbox in datagrid of VB.NET

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VB

Visual-Studio

i have datagridview on my window form of vb.net project. i put following code to call the textbox4 on datagridview of column 3

If Not e.RowIndex = -1 Then
           If e.ColumnIndex = 3 Then
               TextBox4 = New TextBox()
               DgTotalInput.Controls.Add(TextBox4)
               Dim oRectangle As Rectangle = DgTotalInput.GetCellDisplayRectangle(e.ColumnIndex, e.RowIndex, True)
               TextBox4.Size = New Size(oRectangle.Width, oRectangle.Height)
               TextBox4.Location = New Point(oRectangle.X, oRectangle.Y)
               TextBox4.Focus()

from above code i call textbox to datagrid
but to autocomplete i attached column 3 rows data to AutoCompleteStringCollection
i.e.

Dim col As New AutoCompleteStringCollection

and code is

For i = 0 To DgTotalInput.Rows.Count - 2
            col.Add(DgTotalInput.Rows(i).Cells(3).Value)
        Next
        TextBox4.AutoCompleteCustomSource = col
        TextBox4.AutoCompleteSource = AutoCompleteSource.CustomSource

when i type letters in textbox4 it shows suggestions correctly but problem arises when i type letters when textbox in on grid it dont shows suggestions why? and what is solution ?

What I have tried:

Private Sub TextBox4_GotFocus(sender As Object, e As EventArgs) Handles TextBox4.GotFocus
       Dim col As New AutoCompleteStringCollection
       For i = 0 To DgTotalInput.Rows.Count - 2
           col.Add(DgTotalInput.Rows(i).Cells(3).Value)
       Next
       TextBox4.AutoCompleteCustomSource = col
       TextBox4.AutoCompleteSource = AutoCompleteSource.CustomSource
   End Sub