script to add one colum to other

script to add one colum to other

i want to write scrip to add column A to column B and clear value in
column A for next entry ? i have written this script? function
onEdit(event){ var ColK = 11; // Column Number of "K"
var changedRange = event.source.getActiveRange(); if
(changedRange.getColumn() == ColK) { // An edit has occurred in Column K
var state = changedRange.getValue(); var adjacent =
event.source.getActiveSheet().getRange(changedRange.getRow(),ColK+1); //
Add or Subtract Column k's value to/from Column l var coll = coll + colk
break } } } pls help