Default Value to "Category Name" field while creating Requisition

Summary

Default value assigned to the Category Name when entering Purchase Requisitions?

Content

Hello, 

Category Name field when entering Purchase requisitions is confusing for our End Users. We don't use it for anything (our charge account is created based on Expenditure types and orgs). Unfortunately is a required field for any of the Purchase requisition pages. 

Do you know how we can assign a Default value to the Category Name field, so end users don't have to enter it every time? I even tried assigning a value via Page Modification, but it won't recognize it because it comes from a LOV.