Set Value of Field before loading the doctype and donot change the field value on refreshing

Hy Community,
I need to set the value of my custom field in sales invoice before loading the sales invoice
the scenario is in my /app/home i have two shortcuts one is simplified invoice and other is sales invoice both has to load the sales invoice form but if i am clicking simplified invoice the custom_invoice_type field in sales invoice should set to simplified and if i click on sales invoice shortcut it should select the standard, also it should set by session that means if i refresh the form also it should not change the selected value.
This customization is for hiding other not needed fields and section in the sales invoice for simplified