function property/rng update

Does anyone know how to change the property of a function
so that Excel will update when F9 is pressed? I have
written a random number generator sourced on two
parameters (input by the user) as a callable function in
excel. However once the number has been generated and is
in the cell, pressing F9 does nothing (I guess because the
parameters have not changed). So, how do you get Excel to
realise that the function is a rng and so
should 'recalculate' at the press of F9?????

You can record a new macro in excel. Go to Excel. Tools -> Macro -> Record new Macro. You can specify the shortcut key (unfortunately it does not allow function keys, you can use any combination with Ctrl + .. like Ctrl + a, ctrl + f or something). Now you can edit this macro and write your VB code in it. Once you save it and every time you press your key combination, you function code will execute.