OFW + Applescript?

hey, ... and how can I 'insert' a variable into an appleScript?
I mean, what if I want to convert an int to string to use it inside the script or just like a line for every volume changing values?

systemVolumeValueStr = ofToString(systemVolumeValue); //systemVolumeValue is the changing value
systemAppleScript = "osascript -e \"set Volume " + systemVolumeValueStr + "\"";