lack the application for the process

[C# Programming]

I am using this code on combo value change but it's not saving to the XML when the user navigates quickly..
xml_document.SelectSingleNode("/Resume/Detail/ReferencesTitle").InnerText = (string)cboTitle.EditValue;
xml_document.Save(public_var.file_name);

is there any way to lock the application until the above process is completed?