It's a bit urgent... ;)
Someone i know have a Casio calculator (FX-9750 / Grahp35+).
There is in the menu a functionnality TVM with "Days Calculation" that permits to know the number of days between 2 dates.
I have to program for this calculator something very quick but i don't know how to do... i don't know so much about casio programming...
Is it possible to call that TVM -> Days Calculation function inside a program? I can't find any information about that on google... Downloaded some casio manuals but i don't see anything about days calculation...
Please help meee :)
As far as I know you can't call an existing program from CASIO BASIC. I tried finding a way to do that myself, but that was a long time ago with an older calculator, so things could be different now. Still, I couldn't find anything on the internet. In other words, it seems like you would have to implement it yourself.
Here is a tutorial that might be of help for the general programming.
Here is a thread about doing what you wanted in Java that might be helpful (to show the approach to take).
Here is one in C.
Note that you might be able to download a CASIO SDK and write the program in C, if you find that the BASIC dialect is not up to the task. I do not know if your situation permits that, though, nor if such an SDK is available for your particular model.
If you run into trouble I suggest you post a new question.
EDIT: This programming manual from CASIO seems to confirm that it is not possible to do what you wanted, and might serve as a good reference should you choose to implement it yourself. It was made for the FX-9750GII.