This is d sample code for creating customer master.. you can find this sample code from navision help file and there are some others codes too...
.//****
Customer_Service service = new Customer_Service();
service.UseDefaultCredentials = true;
// Creates instance of customer.
Customer cust = new Customer();
cust.Name = "Customer Name";
Msg("Pre Create");
PrintCustomer(cust);
// Inserts customer.
service.Create(ref cust);
//*****
May i know , why you are inserting into General Ledger Entry table...Its Strictly not advisable ......