Psi Notation

I made this notation while trying to simplify an equation involving π's decimal places. Since π has an infinite number of those, I decided to make a notation that would allow someone to get the value of a certain decimal place like the 3rd decimal place in π is 0.001. It is written as $$\Psi_{j=j}^{m}x$$ where j is the first decimal place, m is the last decimal place, and x is any number. If m is equal to j, you don't have to put m or j on the top of Psi.