&optimization_covariable
STRING name = NULL;
STRING item = NULL;
STRING equation = NULL;
&end
name -- The name of the element.
item -- The parameter of the element to be changed.
equation -- An rpn equation for the value of the parameter in terms of the
values of any parameters of any optimization variable. These latter appear in the equation in the
form <element-name>.<parameter-name>, in all capital letters.