Determine the CTLine containg specific character + Core Text + objective c

Question

I am developing an Application in which I am using CoreText for layout purpose. I have used CTFrameSetter to draw the text.I have inserted a blank character '\ufffc' in my text. Now what i want is to determine the position of this blank character i.e. its x, y coordinates. I have not been able to find any function to determine the position of any specific character.

I tried using CTLineGetOffsetForStringIndex( CTLineRef line, CFIndex charIndex, CGFloat* secondaryOffset ); for finding the position, but I couldn't fully understand the working of this method.

Can anyone provide me some pointers on this issue?