customised column puzzle

Hi everyone,

Hope someone can help me with a problem I'm having creating a customised column in Calibre. I have created 3 columns (#plot, #pace and #character) which each contain integer values between 1 and 5.

I now want to create a new column #score which is calculated from the average of the 3 columns. And just to complicate things I want to add a weighting of 1.5 to plot. (i.e. #plotx1.5)

This looks possible but I'm getting lost in the manual. Grateful if anyone can help out.

Thanks!