CONSTANT(varname);      Convert variable to a constant

The CONSTANT procedure causes DAN to treat all subsequent
references to 'varname' as if it were a constant instead of a
variable.  The value used for 'varname' in subsequent expressions
will be its most recently used value; i.e. the last value determined
for the variable in the previous processing period.

This procedure is used for fixing the value of a variable that was
created using the MIN, MAX, AVG, SUM, COUNT, or STD.DEV
functions.
