[horde] Am I using the right application?

[Marvin David Webster]

I am working on a project to develop an interntet based dispatch application using text messages to taxicabs via their cell phones.  The system must be able to check a units calendar to see if a specific time slot is available before sending the automated text dispatch.
 
Can those of you who have had substantial experience developing and working with the Horde suite of products tell me if I am heading in the right direction?  I am currently of the belief that Horde (particularly Kronolith) will give me an open source environment to develop this system, but is going to have a fairly lengthy learning curve attached.  Before I continue, I would like a confirmation this is the correct path.
 
By the way, this is my first attempt at developing an internet based application so I am having to start at ground zero when it comes to things like web servers, etc..
 
Cordially,
 
Marvin David Webster