An instrument variable holds the place of an instrument symbol. You supply the instrument symbol when you use the formula by passing an argument to the formula. All the rules and conventions that apply to instrument constants apply to instrument variables. Instrument variables differ only in that variables are used rather than instrument symbols. Variables are represented using the $# convention, i.e., $1 The dollar sign tells the program that it is looking at a variable, and the number distinguishes one variable from another. (For example, $1 is one variable, while $2 is another). An example of a simple formula containing instrument variables is the following spread: SPREAD1=$1-$2Instrument Variables