General ⇒ Weird Scoping problem

[bongotastic]

I've run into a weird behavior: Given the minimal example below, only the myenv correctly prints the result of \mysum. The only difference between the two environments is the order in which the variable is printed. Can anyone help me figuring how to access the variable in myenv1 in a cell other than the first one of the row?

I am using MikTex, most recent version.
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\documentclass{article}
\usepackage{fp}

% Some command to add to a sum
\newcommand{\addstuff}[2]{#1 & #2 \\ \FPadd{\mysum}{\mysum}{#2}}

% This env doesn't works properly!
\newenvironment{myenv1}
{ \def\mysum{0.001} \begin{tabular}{l l} Item & Qnty \\ }
{ Total & \mysum \\ \end{tabular}}

% This works OK in the end environment statement
\newenvironment{myenv}
{ \def\mysum{0.001} \begin{tabular}{l l} Item & Qnty \\}
{ \mysum & Total \\ \end{tabular}}

\begin{document}

% sum is incorrect
\begin{myenv1}
\addstuff{Apples}{0.1}
\end{myenv1}

% sum is OK
\begin{myenv}
\addstuff{Apples}{0.1}
\end{myenv}

\end{document}