function buildString

Question

Hy everybody,
I need to generate a code.
For example I have a
=>DropDownList wich contains Adult, Child, Infant
=>Textbox which contains MinAge 2,3
=>Textbox which contains MaxAge 14,16 for example
and the field
=> Code  wich is automatically generated
for example if I select Adult, MinAge 2, MaxAge 14 the code should be 00214
(0 for Adult)

Can someone help me?

Thak you