Writing generic profile capture objects into the meter

Hi,

I want to change capture objects into the Load Profile channel 1.1.99.1.0.255 in a meter.

In the meter document it says "Load Profile logger, Attr1 = 1.1.99.1.0.255, Attr 2-3 Access Read, Attr 4 Access ReadWrite, Attr 5-8 Access Read.

So in the light of this, I believe that I can write capture objects with Attr Index 4.

However,

var profileGeneric = new GXDLMSProfileGeneric("1.1.99.1.0.255");
var captureObject = new GXDLMSCaptureObject(4, 0);
profileGeneric.CaptureObjects.Add(new GXKeyValuePair<GXDLMSObject, GXDLMSCaptureObject>(new GXDLMSRegister("1.1.1.8.0.255"), captureObject));

var reply = new GXReplyData();
DlmsReader.ReadDataBlock(dlmsClient.Write(profileGeneric, 3), reply);

throws access denied exception.

I can set the clock with;

DlmsReader.ReadDataBlock(DlmsSettings.Client.Write(clock, 2), reply);

So am I doing something wrong? My data index and attr index is true?