Check out this ASP.NET Scheduler Code Central sample that shows you how to add an appointment using an external combo box:
“How to add a new appointment using the information displayed in a separate control (combo box)” code sample

The sample shows you how to use an external ASP.NET combo box and button to add appointments to the ASP.NET Scheduler.
In the demo, an end-user selects an appointment type using a separate control (ASPxComboBox). To initialize the newly created appointment, the ASPxScheduler1.Storage.CreateAppointment method is used.
Try the above code central sample online here. Thanks!

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