You can use text edits for doing that but it might be a bit boring having to make use of so many #define s.

Then again try google for source of some sales management software and check it out.

Also look into MFC, it provides a lot of things to make using the windows API simple, as long as you are not going for any graphics/cpu intensive stuff.

try hiring a team of developers...

Have them enter data in a real spreadsheet and export it to a text file?

Building a spreadsheet-like interface isn't easy; there are VC products that give you the code for this, I think, for a price.

use GDI function and impliment TextOut function a lot go to http://www.planet-sourcecode.com
you will find some code
refer Charles petzolt book on WIN32 API programming
its difficult but interesting
keep on doing hard work
good luck

Of course it's easy.
Use one of the native OCX controls or simply embed Excel in a window.