Hello,
I recommend you to use the design point table in parametric study option in fluent . First in excel save this plot as .csv file then try to import creating design point table. KIndly follow this user guide link for how to access these options to import these tamperature data from plot and initialise the case without writing udf .This should solve your problem.
42.6. Working With the Design Point Table (ansys.com)
Thanks
Chaitanya Natraj