Cwaist is all the bones gouped so its pivot is in the orgin
rfoot and lfoot are my control foot bones. and im tring to gey the waist to say inbetween the feet. so when i move a foot forward the body stays inbetween rfoot and lfoot.

here is my expression

Cwaist.tx = (rfoot.tx + lfoot.tx)/2;
Cwaist.ty = (rfoot.ty + lfoot.ty)/2;
Cwaist.tz = (rfoot.tz + lfoot.tz)/2;
Cwaist.ry = (rfoot.ry + lfoot.ry)/2;

here is my error

expression -s "Cwaist.tx = (rfoot.tx + lfoot.tx)/2;\r\nCwaist.ty = (rfoot.ty + lfoot.ty)/2;\r\nCwaist.tz = (rfoot.tz + lfoot.tz)/2;\r\nCwaist.ry = (rfoot.ry + lfoot.ry)/2;" -o "" -n "Cwaist_expression" -ae 1 -uc all ;
EEnodeAdded Cwaist_expression;
// Error: More than one attribute name matches. Must use unique path name: rfoot.tx //
// Error: More than one attribute name matches. Must use unique path name: lfoot.tx //
// Error: More than one attribute name matches. Must use unique path name: rfoot.ty //
// Error: More than one attribute name matches. Must use unique path name: lfoot.ty //
// Error: More than one attribute name matches. Must use unique path name: rfoot.tz //
// Error: More than one attribute name matches. Must use unique path name: lfoot.tz //
// Error: More than one attribute name matches. Must use unique path name: rfoot.ry //
// Error: More than one attribute name matches. Must use unique path name: lfoot.ry //
EEnodeRemoved Cwaist_expression;

im at a loss i have no idea what im doing wrong. Thanks.