[TYPO3] EXT development

[Rocky]

Hey,

I have 6 TYPO3 websites up and running on my server. There's a stand 
alone small php application which collects new clients' information and 
store them into a database table. The reason why we did not using EXT 
but used stand alone php is that we were not familiar with TYPO3 at that 
time. we would have already put all 6 website into a single TYPO3 
installation if only we had really being familiar with TYPO3. Anyway, 
now the client's ask us to develop another application which his workers 
can add their clients' information if their clients are not 
computer-literated. So basically the clients' information database table 
has 2 places where the data come from. 1 from stand alone php 
applications and another from the new application. We are thinking of 
develop an EXT for the new application since it requires user privilege 
configuration not all his workers will be able to see all the clients 
information.

Is that possible I create an extension which renders an HTML forms and 
store the submitted information into external database table? If this is 
doable can any of you give me some hint please?

Thanks,
Rocky