for creating a phase diagram with Matlab, Excel or other Windows applications you may consider a process library,
we discuss Prode Properties in this EGPET thread

'http://www.egpet.net/vb/threads/27092-Excel-library-for-process-calc-s-including-distillation'

Prode Properties allows to draw vapor-liquid-solid phase diagrams (or phase enevelope) in Excel, Matlab etc.
examples are
-vapor-liquid
-vapor-liquid-liquid
-vapor-liquid-solid
-...