secure server for client scheduling

[rte123]

I am a professional who keeps client records on a computer. Both I in my office and an associate in another office wish to schedule clients on a common scheduling form, nearly simultaneously if possible. I have Win XP Pro and I have looked at the remote desktop instructions, but I have questions before I set up a server. First, I have never done so and I would appreciate any general tips. Second, I have SBC Yahoo high speed internet (DSL) and, although the encrypted access to my router is fairly secure, I understand, I wonder about the security of this web based sharing of confidential data that comes into play with setting up a server host and peripherals. Third, I am curious if more than one party can enter data into a scheduling form simultaneously or, if not, how much lag would there be between the two parties doing so consecutively but nearly simultaneously. I am most appreciative in advance to anyone who has experience with this and wishes to reply.