Is it possible to do something like this:
var s:String = format(\"%20d %-10s %s\", time, type, message);
In languages like C, C++, C#, Python,
You probably are looking for mx.utils.StringUtil.substitute(). Works similar to .NET String.Format().
For Example:
StringUtil.substitute("Hello {0}", ["World"]);
Adobe Livedocs for StringUtil class