looking for something like isearch-forward-column

[Joel Graber]

I use gnu emacs version 21.2.1 usually on linux redhat system.
to view very wide column oriented datafiles 
I'd like to be able to isearch forward and backward for
a character in the same column as the cursor.

I've googled and found several similar questions in *emacs* 
groups but no satisfactory answers.

My latest direction is to start by making it a macro
to call isearch-forward-regexp ^...<letter>

Example text file:
0123
LLLxLLLLL line 1
LHLLLLLLL line 2
LLLLLHLLL line 3
LHLLLLLLL line 4
LLLHLLLLL line 5

If my cursor is on the x in line 1 column 3.
and I want to find where is the next H in this column
(which is in line 5)
and I press a key bound to a macro,
I need it to query me what character to search for,
then convert it a call to isearch-forward-regexp 
for string ^...H

How do I insert <current-column>-1 number of .
into the regexp in the macro?

Or is there lisp code to support this already maybe?

thanks,
-- 
Joel Graber