Baselines estimates

[CanadAL]

Hello community,

I've done some searching (Googling) and went through all the posts I thought were relevant on the Atlassian community but I couldn't find an answer to my strange question.

Use case scenario:
As a PM, I need to have a baseline estimate that is separate than the original estimate, so that we can gauge how accurate our baseline estimates were when initially scheduling.

The baseline estimate is created/entered at the project scheduling stage (many of our large bodies of work and sometimes the stories are defined in advance). When the piece of work (Story, Task, etc.) reaches the person(s) doing the work, they provide the original estimate (the built in functionality of JIRA). In the future, we would compare our baseline estimate to the original estimate to see how far off we were and better plan our project schedule (timelines).

Questions:

I find that there isn't a built in a to add a new "estimate" field (since the original estimate is part of time tracking, which is a system field). While I can add a text field, it doesn't have the fancy calculations (i.e., knowing if it's a week, day, hour, minute when you enter 'w', 'd', 'h', 'm' along with your numbers).

1. Any suggestions on how I can create such a field (baseline estimate)?
2. Any suggestions on how I can create another field that will calculate the difference between the baseline estimate and the original estimate (to determine how far off our estimates were)?

Any help would be much appreciated. Please go easy on me...this is my first post. :)