Your task to move files from one state to another should have a line to add notes to the History. If you are populating that note with the EC number you can use the Search Tool to find that number in the History. This is the way I do it anyway.
You can also search for files that have moved to a specific state before/between/after certain dates and/or by a certain person.
Thanks Steven, But I meant through the API.
I'm not looking for which file has gone through a transition, but rather which file initiated the transition from the code itself so i can extract data from the file. or
An example would be that the ECO has some information such as a file name and revision, and I would like to extract it from there to do further manipulation and the desired files.
Another example would be to log information such as delays (KPI or performance indicators). the ECO has all the dates, and the referenced files as well, but I only need the ones from the ECO.
You'd need to hook into EdmCmd_PreState or EdmCmd_PostState. Have a look at the API help file.