Contional productions

[Vidhya]

Hi All

Can I write conditional productions based on a flag .

I have a normal production ,then inside the action part I determine the
value of the flag .

After that I  want the productions itself to be controlled by this flag .

Some thing like 

If (flag == true) 

Then this production 

Else

Some other production

Is this possible

 

Please let me asap

Thanks