[kinook]

There are several ways to accomplish that (the preferred method would probably depend on your needs). Some are described here:
http://www.visualbuild.com/Manual/hints.htm

One way would be to pass them on the command-line to VBP:
http://www.visualbuild.com/Manual/consoleapp.htm
http://www.visualbuild.com/Manual/command_linegui.htm
in a batch file, then call the batch file in the scheduled task

Another way would be to create them as temporary macros
http://www.visualbuild.com/Manual/macrostab.htm

and save those to a file via a Run Script (VBScript) step like:

Application.Macros(vbldMacroTemporary).Save "%PROJDIR%\name.macros"

Then, at the start of your project, load the temporary macros:

Application.Macros(vbldMacroTemporary).Load "%PROJDIR%\name.macros"

http://www.visualbuild.com/Manual/runscript.htm
http://www.visualbuild.com/Manual/objectmodel.htm

Either way, those macros could then be referenced in your project (i.e., %MACROA%) as needed.

You can also use the technique shown in the VisBuildPro.bld sample to define defaults as project macros, and override those via temporary macros as needed.
http://www.visualbuild.com/Manual/visbuildprosample.htm