How to enter text in a particular field within an already open program

Here is the scenario...

My office has started using Microsoft Project and we want to link up specific tasks with the offices own time tracking software (it lets you log what you did and how long it took you to do it...for payroll purposes). What I want to try to do is make the tasks a link and when it's clicked on, to open up our own software and enter in the specific tracking number for that task in a specific field so it brings up our own record of it so we can record what has been done and track the time worked on the task.

Any suggestions on how to go about this? Not sure what language I should use or where to begin with this.

Thanks for any help in advnace