Use sp_drv_text_locator_valid which accesses
        locator_valid.
Syntax
        
        
          sp_drv_text_locator_valid locator
         
       
Input Parameters
        
        locator – the text_locator to validate.
       
Output Parameters
        
        A 
bit representing one of these values:
- 
              
0 – false, locator is invalid.
             
- 
              
1 – true, locator is valid.