Help needed creating a program

Hi
I am a newbie.

I have a task at work to create a “program” using excel.

What is required:

I need it so when the program is opened it opens in excel but the dialog worksheet.

I require it to allow user to input information into various fields (for example the tasks they have performed) and then they can submit it by pressing OK.
This will then confirm the message and then place this into the various fields within the main excel worksheet (not viewable by the users).

I understand this is difficult and may take a lot of coding but can anyone steer me in the right direction.

For information I am using MS Excel 2003.

Regards

Steve