The text selection as character by character using SDK function

In one of plug-in application, I want to perform text selection and in that I want to allow user to select text as character by character (Acrobat itself will allow you to select only the characters), but sdk fucntion not allowing me to develop like that, here the text selection is always of whole words, not part of
words.   Is there a way to achieve that functionality(to selecte the desired part of the text), any SDK funciton available to set that option,  please let me know.

thanks,

Palaksha