NumMin  - script and chart function
                Returns the lowest numeric value of 1 to N arguments. If no numeric value is found, NULL is returned.
Information noteThe nummin function has been superseded by the RangeMin - script and chart function function. Although nummin can be used, it is not recommended.
                Syntax:
NumMin(expr1 [ , expr2, ... exprN ])
Examples and results:
- nummin( 1,2,4 ) returns 1
 - nummin( 1,'xyz' ) returns 1
 - nummin( null( ) 'abc' ) returns NULL