Please. How to add an equation to a note?

I mean.. I've make a block note with a weight PDM property vinculated, and I need to increase this value over 4%. The only way I think it is possible is to writing a kind of equation (In the note) like   \$PRPVIEW:{Weight}*0.04+\$PRPVIEW:{Weight} but it doesn't work for me please somebody helpme.

Sorry 4 my english