[amibroker] 'CategoryRemoveSymbol' dosn't remove symbols.

[directaim]

I want to empty a watch list.
But all symbols remain in List 1,
wether I use at the beginning of my scan the statement:

CategoryRemoveSymbol( "", categoryWatchlist, 1 ); 

or the statements:

for(i=1;i<BarCount;i++)
{ 
   CategoryRemoveSymbol( "", categoryWatchlist, 1 ); 
}  

or the statements:

for(i=1;i<BarCount;i++)
if( LastValue( V ) > 0 ) 
{ 
   CategoryRemoveSymbol( "", categoryWatchlist, 1 ); 
}  
.

What am I doing wrong?

[Note: CategoryRemoveSymbol is AFL 2.5 which my AB version does 
handle]