Re-Select previously selected layer in custom action

Hi,

I would like to create a custom action in Photoshop which is supposed to do the following steps:

1. Select group "overlay-main"

2. Set its opacity to 50%

3. Select the layer (or group) which had been selected when the action was triggered (i.e. before step 1).

Is something like that possible with actions? An alternative would be an action-step which changes the opacity of a specific group ("overlay-main" in my case) without selecting it, i.e. without changing the layer selection at all. Is that maybe possible?

Or would I have to use the plugin API and write a plugin to achieve something like that?

Thanks,

Jan