Data Types\Number\ Expression

This node can evaluate an expression, then
 
the result of this  evaluation can be used to activate other responses. 
Example
In the example below when the "Import_UPS" geometry is clicked "Evaluate Number Expression" is executed. The expression is simple math.sqrt(16), and the result is linked to the "Set Number Variable" node, in "result" variable.  This variable is then linked to a "Variable Writer" to display it.