I have a project that i need to send some data with an RS232 to USB cable from external Msp430 launchpad to the computer and fake it as a mouse. Is this possible without learning USB protocols of the mouse?
You could pretend to be a Microsoft Serial Mouse: http://paulbourke.net/dataformats/serialmouse/
Edit: if that doesn't work, and the computer has a PS/2 mouse port, you can use that: http://www.computer-engineering.org/ps2protocol/
Otherwise you're going to have to get a microcontroller with USB support and learn that, which will be time-consuming.
Microchip has a PICDEM Full Speed USB Demo Board for this. This demo board comes with a program that emmulates a HID mouse using USB. You could adapt this program to create your fake mouse.