Park And Post Workflow ,Need to Deactivate the post button in FBV0 for documents which are in unreleased state on parking

We are using customized Workflow for Park and Post Process.

Currently the authorized user to post documents is able to post the document directly from FBV0, even though the document is in parked and unreleased state.

But the requirement is to control this.We need to do posting through workflow only.

We looked into the solutions provided in SCN and tried configuration in OBWA and OBWJ.

But we already have a workflow for payment and advise for which variant is already configured in OBWJ for a company code.

Now in OBWJ I am not able to configure Park and Post Workflow Variant for the same company code as for a particular company code

only single workflow variant can be configured.

Please suggest how to fulfill this requirement.Is there some way through which we can do multiple variant configuration to a single company code.

Also is there any alternate to solve this issue.

This is urgent issue.Kindly help.

Thanks in advance.

Prashant