An appropriate input form to capture details

Question

Hi
I have a C# programme that captures client details for reporting purposes.  What I would like to do is have some kind of input form that can be sent by users to clients.  The idea is that once the clients have entered their detials and sent them back to the user, the user can then load the details into the C# application. 
I have looked into the following ideas but have had limited success implementing them:
1.  Send a word xml form(with an xml schema attached) which can then have its xml data read by the app once completed.
2.  Send an html file with an input form which can then save a return the details as an xml file(and then obviously read in by the app).
The information will be sensitive so encyrption of some kind would definatly be required. 
Can anyone give any recommendations on how to accomplish my goal or on how I can successfully implement the above to options?
Thanks