This rather small document

\documentclass{article}

\usepackage{calculator}

\newcommand{\myPerCent}[2]{%
\DIVIDE{#1}{#2}{\sol}%
\MULTIPLY{\sol}{100}{\sol}%
\ROUND{\sol}{\sol}%
\sol%
}

\begin{document}
Computed \myPerCent{2441}{8667}.\par
\end{document}

produces this warning (I guess it's a warning and not an error as the PDF is finally built):

(\end occurred when \ifdim on line 13 was incomplete)

I have no clue how to solve the issue as the code looks ok at first glance, but it seems something is off here.

How can I use the package in a proper way?

(I'm quite happy I was able to identify the source for the warnings at least as the original document is rather large and I started looking into things like How to diagnose unclosed (incomplete) \iftrue or \ifnum? but somehow I didn't get me anywhere and I don't seem to know anything more than before...)