Whats wrong with this code for database insert?

[twsaustralia]

Public Class Customerdetails
Inherits System.Windows.Forms.Form

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
updatecustomerdatabase("Insert INTO Customer (FirstName), VALUES cstr(txtcustomername.text)")

End Sub
Sub updatecustomerdatabase(ByVal sqlStr As String)
Dim newcustomer As New DataTable
Dim connStr As String = "Provider=Microsoft.Jet.OLEDB.4.0;" & _
"Data Source = maindatabase.mdb"
Dim dataAdaptor4 As New OleDb.OleDbDataAdapter(sqlStr, connStr)
dataAdaptor4.Fill(newcustomer)
dataAdaptor4.Dispose()

End Sub
End Class

[Metalzed]

Public Class Customerdetails
    Inherits System.Windows.Forms.Form
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        updatecustomerdatabase("Insert INTO Customer  (FirstName), VALUES cstr(txtcustomername.text)")
 
    End Sub
    Sub updatecustomerdatabase(ByVal sqlStr As String)
        Dim newcustomer As New DataTable
        Dim connStr As String = "Provider=Microsoft.Jet.OLEDB.4.0;" & _
                                "Data Source = maindatabase.mdb"
        Dim dataAdaptor4 As New OleDb.OleDbDataAdapter(sqlStr, connStr)
        dataAdaptor4.Fill(newcustomer)
        dataAdaptor4.Dispose()
 
    End Sub
End Class

I am not sure
But it could be this

"Insert INTO Customer (FirstName), VALUES cstr(txtcustomername.text)"

is not a proper SQL query.
is txtcustomername a textbox?

then the row
updatecustomerdatabase("Insert INTO Customer (FirstName), VALUES cstr(txtcustomername.text)")

should be change to
updatecustomerdatabase("Insert INTO Customer (FirstName), VALUES '" + cstr(txtcustomername.text) + "'")

notice the '
hope this was a help.