To access a (raw) macro value from script code:
Application.Macros(vbldMacroTemporary)("ABC").Valu e
or
vbld_AllMacros()("XYZ").Value
http://www.visualbuild.com/Manual/macrosproperty.htm
http://www.visualbuild.com/Manual/sysscriptmisc.htm
Or, to expand the macro's value (any macros or script expressions it references):
Application.ExpandMacrosAndScript("%MYMACRO%")
http://www.visualbuild.com/Manual/scripteditor.htm
http://www.visualbuild.com/Manual/specialchars.htm
In the case of FAILSTEP_NAME, it's more direct to just use the FailedStep object (FailedStep.Name) rather than that macro.
http://www.visualbuild.com/Manual/objectmodel.htm