If you want to use optional segments, press F1 while VoiceAttack has focus to open VoiceAttackHelp.pdf in your default PDF viewer, and search for "Dynamic Command Sections".
You'll also want to have a look at the "{CMD}" and/or "{CMDSEGMENT:}" tokens, along with the "Begin a Conditional (If Statement) Block" action, which allow you to have a command execute different actions depending on what is spoken.