"Limn®:The Flowsheet Processor" is a flowsheet solution and mass balancing software package that runs within Microsoft Excel. As most engineers are familiar with Excel, this means that Limn is extremely user friendly, eliminating the need to learn to use a new software package. Limn uses model and structure template Wizards to generate Excel workbooks with a formal, fixed structure, allowing Limn models to be shared more easily amongst different users. The structured approach used by Limn also improves rapid trouble shooting while minimising the chances of loss of intellectual property when employees move on. The ability to generate a flowsheet quickly in Excel and to then be able to use it in other formats (e.g. linked to PowerPoint or Word), enables the user to generate visual representations of a problem to assist non-technical people with their understanding. Limn embodies a very powerful approach to mass balancing and the ability to easily create and record multiple scenarios makes the software an extremely worthwhile addition to any process engineers "toolbox". Limn has been designed to be totally customizable. Existing unit icons, unit models and Wizards are easily modified, or new examples created. Due to the "open" nature of the software and its integration within Excel, companies can completely customize Limn to suit their individual needs. Limn has been proven in many user case scenarios, where the value added has far exceeded the original purchase cost of the software.