lt as unformatted string, 'html' to render it as unescaped html, 'text2br' to convert line endings like '\r', '\n' or '\r\n' to HTML breaks or 'script' to just execute as JavaScript w/o displaying anything.
* @param {formula=VAR} any valid JavaScript expression with following variables and aggregate functions (optional, default: VAR)
  - VAR1, VAR2, ... represent the corresponding item's value, VAR is an array of all item values
  - SUM(VAR), AVG(VAR), SUB(VAR), MIN(VAR) and MAX(VAR) aggregate the values
* 