registrer action plug-in of illustrator

During start up, you need register the action like so (rough code):

AIActionParamTypeRef actionParameters = 0;
AIErr error = sAIActionManager->AINewActionParamType(&actionParameters);
// add parameters using AIActionSetType
// register action with RegisterActionEvent & actionParameters
// clean up when done
sAIActionManager->AIDeleteActionParamType(actionParameters);

Next, when you are about to execute the functionality you described when you registered the action, you check to see if the user is recording:

if (sAIActionManager->InRecordMode()) {
     AIActionParamValueRef valueBlock;
     AIErr error = sAIActionManager->AINewActionParamValue(&valueBlock);
     // e.g.
     sAIActionManager->AIActionSetReal(valueBlock, 'valu', 10.0f);
     sAIActionManager->RecordActionEvent("my_action_name", kDialogOff, valueBlock);
     // clean up
     sAIActionManager->AIDeleteActionParamValue(valueBlock);
}

Now the action has been recorded. It should show up in the Action panel.

Lastly, when the user plays the action, you'll get a call/selector of kActionCaller / kDoActionSelector (see AIActionManager.h). When you get that, you need to cast the message void* to a DoActionMessage. It has a AIActionParamValueRef member param, from which you pull out the action values:

DoActionMessage* doActionMessage = reinterpret_cast<DoActionMessage*>(message);
AIReal value = 0.0f;
AIErr error = sAIActionManager->AIActionGetReal(message->param, id, &value);
// pull out other parameters if there are any
// do your functionality!

There are a bunch of other parameters with registering & recording actions you should play with. You can record enums, for example, which let you store a value like '10' with a string to describe it. You can also specify whether or not your functionality has a dialog or not, and let the action indicate if they want to show your dialog or not (they want to stop and tweak action parameters halfway through a playback).

Hope that helps!