To Check is a Field is populated by F4 help or Manually.

HI Folks,

Need help to Check if a Field is populated by F4 help (Search help) or Manually in a Module pool program.

Basically the search help already contains all validation required for the field,so if i get to know that the user has selected value from F4 Popup i need not validate the value entered but when user had a manually populated the field i have to validate it with some conditions.