EXECUTE stored procedure from external app

I am setting up some email marketing software called Campaign Enterprise. It requires an ODBC connection into FileMaker, in this case. The software has the ability to run stored procedures or SQL statements.

In this case I am trying to write a procedure to compare the current record in the email software to those in a table in FM, if there is a match, it will increment a field value by 1 in there is no match it will create a new record in the table and insert a uniqueid.

I have successfully used 2 different sql statements to either create a new record and insert the data or to update an existing record, but I cannot seem to combine them into one IF THEN ELSE statement, so I was told I need to write a procedure that I can execute.

Would a stored procedure be a script in FileMaker that I can execute from another program through odbc, or is there something I am missing? Does anyone know how to do this?