Find the tab stop position

I'm sending output to a text file and to make this file more readable, I indent some lines by placing one or more vbTab characters at the beginning.

In some of these lines, I'd like to add a specific character ('x') just to the left of the tab stop position. How do I know how many blanks are there to the tab stop position?

Of course, I can use various spc characters instead, but I'm curious to know if the tab stop position can be retrieved.