[amibroker] How to use TimeFrameSet in plugin dll

[tiedemj]

Executing the following code on a 15 min bar chart returns the same value for 
gSite.getArraySize()

arraySize = gSite.GetArraySize(); //returns bars in 15 min chart

AmiVar args[ 1 ];
args[0] = makeAmiVarFloat(3600); //proper amibroker var
gSite.CallFunction("TimeFrameSet",1,args);

arraySize = gSite.GetArraySize(); // still bars in 15 min chart

also, if I try to change timeframe in AFL code:

TimeFrameSet(3600);
myPlugin();
TimeFrameRestore();
myPlugin();

a call to gSite.GetArraySize() returns the same value in both calls to 
myPlugin(); Also the build in variable "barCount" returns the same value. What 
am I doing wrong?

Best regards
Jens