Create a selection at specified scrollHeight

[CaptainSensible]

Hello,
I would like to highlight a paragraph in a page (similar to the result of 3 clicks on a text), and all I know is the scrollHeight of the document where the textrange must be selected. Is this possible???
Thanks in advance.

 

[CaptainSensible]

No response?
ok, maybe I'll try to explain another way:
I have a text in a left frame, at a scrollheight and I align a second text from right frame.
if left text current scrollheigth is at 20% of total text, I position right text at 20% of total right text.

Now, I want to highlight the paragraph situated in the middle of the second frame, like 3-clicks on the paragraph.
How can I get this textrange?