For Approval Management, for setting default approval procedure, you need not to go for the development. You can set this up by means of Rule Policies,
Rule Poilicies are simple If .. Then.. conditions which set the approval procedure. You can have a rule policy say, If Txn Type is ZMCR Then set rule policy as APP_PROCEDURE_1 something like this.. Pls give it a try and let me know if it works for you.
-Vivek