How to define a `multiple prompt' function?

[Rodolfo Medina]

I wish to define a function that prompts me more than once: let's call it
`my-function': when I type `M-x my-function', in the echo area I see (just an
example):

 Hi, how are you today?

.  Then I type, e.g., `fine RET', and again it prompts me with:

 I see.  And, what did you do yesterday?

... and so on.  Then I'm going to put some `if... else' conditions over my
possible answers.  Can anybody please provide some hints about how to elisp
this?

Thanks for any help
Rodolfo