You said that you only can preview data on data grid when you load your form.
So the code that you using to preview data at load form, make it like procedure/function.
You just call the function to refresh datagrid from anywhere.
After insert, edit or delete data or on refresh button.
Just put your preview code into procedure/function
Public Sub RefreshDataGrid()
... 'Your query to preview data on datagrid
You can call that procedure at any event to refresh data grid
Private Sub btnAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAdd.Click
... 'your code to insert data
RefreshDataGrid ' call refreshdatagrid function to refresh data on datagrid after insert statment
Do the same thing for edit or delete event or refresh button.