CDF_VARNUM function returns the
variable number associated with a given
variable name in a Common Data Format file. If the specified variable cannot be found in the CDF file, CDF_VARNUM returns the scalar -1.
Result = CDF_VARNUM(
The CDF ID, returned from a previous call to CDF_OPEN or CDF_CREATE.
A string containing the name of the variable.
A named variable into which CDF_VARNUM will place a 1 to indicate that the referenced variable is a zVariable or a 0 to indicate that it is an rVariable.