Hi
Intellectual property can be a very tricky area. Whilst the spreadsheets / VBA were your creations built using your knowledge, you also have to consider that your employer paid you for your time. And they possibly paid for you to learn, so there has to be a bit of give and take.
Don't get me wrong - I'm not taking sides with the employer because I also empathise that had you not done what you did, then it would have cost your employer a lot more. Is your employer aware of what you have done?
Correct me if I'm wrong here but it sounds like you want your employer / co-workers to acknowledge, or show some appreciation, for what you have done. Unfortunately you aren't the first person to feel this way and you definitely won't be the last.
Now I'm not a career counsellor or anything like that, but it sounds like you may need to get into some dialogue with your boss and / or co-workers. I can't tell you what to say or in what context but there will be ways and means of achieving this without appearing big-headed. If that doesn't work then you may want a small splash screen to appear on some of your creations to remind everyone exactly who created these spreadsheets.
But seriously, the best thing you can do here is to learn :
a) from your mistakes (ie don't get into this same position again), and
b) as much as you can as quickly as you can. If it is at the expense of the employer then all the better. If you are the highest skilled member of the team when it comes to VBA etc then you will be valued / revered (maybe not indispensible because no-one is, but close enough). So take the chance to learn even more.
Also keep in mind that your co-workers will not have the experience with / intimate knowledge of the inner workings of the spreadsheet to fix any problems that may arise. Just wait and see - give it enough time. Then you will be valued and appreciated.
Chin up and good luck!
Cheers, Andrew