Custom Function To Auto Assign A Task Template to Request

Custom Function To Auto Assign A Task Template to Request

Hello,
I'm new to custom functions and attempting to write a custom function that looks at the "request type" assigned to a new request and automatically assigns a specific task template that has been created. 

Request Type = PIT Training/Certification
Task Template = New Powered Industrial Truck (PIT) Operator - Training/Certification Requirements 

Could anyone assist with writing a custom function for this?