Formatting a gridview bound to a data table

Ok I am binding a gridview and a datatable and I dont know how to set the dataformatstring of the gridview to $.  

Like This:
        Dim table As New DataTable
        table.Columns.Add("Category")
        table.Columns.Add("Year Total")
        table.Columns.Add("Year Left")
        table.Columns.Add("Month Total")
        table.Columns.Add("Month Left")
       
        Dim row As DataRow = table.NewRow()
        row("Category") = "Food / Groceries"
        row("Year Total") = a1.ToString
        row("Year Left") = a1yleft.ToString
        row("Month Total") = a1m.ToString
        row("Month Left") = a1mleft.ToString
        table.Rows.Add(row)
        Dim row2 As DataRow = table.NewRow()
        row2("Category") = "Household / Maintenance"
        row2("Year Total") = a2.ToString
        row2("Year Left") = a2yleft.ToString
        row2("Month Total") = a2m.ToString
        row2("Month Left") = a2mleft.ToString
        table.Rows.Add(row2)
        Dim row3 As DataRow = table.NewRow()
        row3("Category") = "Program / Other"
        row3("Year Total") = a3.ToString
        row3("Year Left") = a3yleft.ToString
        row3("Month Total") = a3m.ToString
        row3("Month Left") = a3mleft.ToString
        table.Rows.Add(row3)
        GridView5.DataSource = table
        GridView5.DataBind()