How to unchecked the datagridview checkbox.

I added a checkbox and a new column to the datagridview. The checkbox is being checked automatically when adding data to this column. If we delete this data thinking it is not necessary
The checkbox is still checked. I mean, once I give the data, the checkbox must be checked, but if I remove this data, how to unchecked the automatic checkbox
Goes.
I am making this effort on VB.net.
Thanks in advance to the experienced collaborators.

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim checkboxcolumn As New DataGridViewCheckBoxColumn()
checkboxcolumn.HeaderText = "*"
checkboxcolumn.Width = 20
checkboxcolumn.Name = "checkboxcolomn"
DataGridView1.Columns.Insert(0, checkboxcolumn)
End Sub

Sub display_data()
Dim cmd As New SqlCommand("select * from tbl_Pro", con)
Dim da As New SqlDataAdapter(cmd)
Dim dt As New DataTable
dt.Clear()
da.Fill(dt)
DataGridView1.DataSource = dt
dt.Columns.Add("Qty")
End Sub
Private Sub DataGridView1_CellValueChanged(sender As Object, e As DataGridViewCellEventArgs) Handles DataGridView1.CellValueChanged
Dim cell1 As DataGridViewCheckBoxCell = DataGridView1.Rows(e.RowIndex).Cells(0)
cell1.Value = True
End Sub