How to allow only decimal numbers of datagrid cells in vb.net

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VB

WinForms

Hi guys, I have a datagrid and add the columns dynamically like this,

create_column(pTable, "LeaveType", "string", False, "LeaveType", True, True, 50)
create_column(pTable, "TotalLeaves", "double", False, "TotalLeaves", False, False, 50)
create_column(pTable, "Year", "string", False, "Year", False, False, 50)

'Add Empty values to the table
con = GetCon()
con.Open()
Dim qry As String = " SELECT LEAVETYPE FROM LEAVETYPE"
Dim cmd As SqlCommand = New SqlCommand(qry, con)
dr = cmd.ExecuteReader
Dim nr As DataRow
While dr.Read
nr = pTable.NewRow
nr.Item(0) = dr(0)
nr.Item(1) = "0"
nr.Item(2) = ""
pTable.Rows.Add(nr)
End While

dGridView.DataSource = pTable
dr.Close()
con.Close()

Public Sub create_column(ByVal dt As DataTable, ByVal col_name As String, ByVal col_type As String, ByVal autoincr As Boolean, ByVal caption As String, ByVal read_property As Boolean, ByVal unique As Boolean, ByVal length As Integer)
       Try
           Dim dtcol As New DataColumn
           If col_type.CompareTo("string") = 0 Then
               dtcol.DataType = System.Type.GetType("System.String")
               dtcol.MaxLength = length
           ElseIf col_type.CompareTo("double") = 0 Then
               dtcol.DataType = System.Type.GetType("System.Double")
           ElseIf col_type.CompareTo("integer") = 0 Then
               dtcol.DataType = System.Type.GetType("System.Int32")
           End If
           dtcol.ColumnName = col_name
           dtcol.AutoIncrement = autoincr
           dtcol.Caption = caption
           dtcol.ReadOnly = read_property
           dtcol.Unique = unique
           'Add the column to the DataColumnrow_tuple.
           dt.Columns.Add(dtcol)
       Catch ex As Exception
           ''MsgBox(ex.ToString)
       End Try

only total leaves column should allow decimal or numbers in datagrid. By default total leaves column of rows zero's.

initially :
by default.
totalleaves
0
0
0


i need only adding the decimals numbers .

Please any one help me..