coding advice for my async/timer function in vb.net

Hi experts,

I need advice on using an async function  or timer in the following situation (vb.net)

a) the programm calls a function, which returns a result <long>
b) it gives the function n seconds to return the result, so it waits for the result.
c) if the result returns between 0 - n seconds its ok, proceed with the result
d) if the result does not returns return a message ....

Thanks