OnClick and OnClientClick issues

I have situation where a client goes to a website to complete a webform and upon submission/click of an asp button performs two acts: 1) runs a jquery script that opens an iframe for an embedded form to a thirdparty service that gets information via a url created by the jquery also (in this case docusign) 2) runs a method to insert specific data about the submission to an sql database table. It is my understanding that the OnClient has to fire prior to the OnClick as well as some sort of return/postback if I understand correctly is needed to fire the onclick/severside method. So my difficulty has been trying understand how best to get the serverside method to fire... I understand how to do one or the other but cannot seem to get both to work as the iframe when finished has its own landing page set by docusign. So currently my asp button OnClientClick calls the following jquery that opens an iframe... I cannot figure how to also have it also cause the Onclick event to fire as well while the client if finishing their work through the iframe? jquery used is attached.