How to gray out a line in the ALV output so that the user cannot sel line?

Hi Friends,

I have an ALV report. When it is executed, I have provided the user an option of picking multiple lines(output) and click on the the pushbuttons(this is a workflow report...there are 3 push buttons APPROVE, FORWARD and REJECT). When the user clicks on the APPROVE push button, I call a method to post the invoice. Once the invoice is posted, the user should not be able to pick this line again. How do I gray out this output line that way the user is not allowed to pick this line again. It could be multiple lines too..

Thanks