[amibroker] BarsSince(Buy) >= 300 NOT resulting in a Boolean?

[gariki]

I am trying to put in this line of code

  if( LongEntryPrice > 0 AND (BarsSince(Buy) >= 300 ) )

and its giving me a compile time error saying:
Error .
Condition in IF, WHILE, FOR statements has to be a Numeric or Boolean
type.. for the BarsSince function.

BarsSince(Buy) should return a numeric value and comparing it with a
number should return a boolean value.

Does anyone know why it is showing up as error?

Thanks
-gariki