I often have to manipulate Excel and CSV spreadsheets to prepare data being imported into MySQL. I need to do things like find and replace values, insert and remove columns, sort rows, etc. I currently use NeoOffice and have used Excel. I've found, however, that both of these applications, in the spirit of being "helpful", often mangle data. They reformat date and time fields, they reformat numbers, try to convert strings to numbers, etc.
Is there a program that I can use to edit spreadsheets that will not try to second-guess data types? That will just leave the values alone? What I'm after is something like a plain text editor for spreadsheets. Bonus points for Mac compatible applications.
Alternately, have I just missed some settings in NeoOffice that will turn all this "helpful" formatting off?