Hiding in code is a matter of password protecting. The only way (supposedly) to open the coding is with the password.
On a sheet, that is a different story. A simple method is to put the font at the same color as the background. However, if someone selects more than one cell, the font will be visible. Another method is to hide the cell (row or column). The problem with this is that you can still go to the cell and either unhide it, or see the contents in the formula bar. Your best bet is several steps:
Unlock the cells that will not have the password;
Check both the locked and hidden boxes for the cells that will have the password (hidden disallows viewing contents in the formula bar);
Password protect the sheet.