How to disable the workflow button on Purchase Requistion form after submit

Hi All,

I checked with the functionality of workflow on Purchase requisition form, and I found there is a method

canSubmitToWorkflow, which we can use to enable/disable(or to say visible/hide) the workflow group.

But, if the workflow is submitted, and then I want to show/hide the workFlow group, is somebody have any idea, how can i do that…

I dont find any reference method on form for that. Any idea is appreciable…

Thanks in advance…