Conditional formatting for print button
I have a button called print, which runs a script that prints out my invoice layout. I need to set the conditional formatting of the button (i think that's how to do it, anyway) so that once the button has been pressed for an individual record, the font color changes to red so that i can look at a customer's invoice and tell whether it's been printed out already or not. I cannot figure out how to create the formula that will do this. HELP!!