Spreadsheets are a widespread tool for a variety of tasks, particularly in business settings. Spreadsheet users employ a form of programming that, while popular, has been shown to be highly error-prone and with limited expressiveness. An important approach to augment spreadsheets is to provide logic knowledge representation and reasoning (KR&&R) functionality. In this paper we present LESS (Logic Embedded in SpreadSheets), a system that integrates PowerLoom, a highly expressive logic KR&R, with Microsoft Excel. LESS’s design provides different tiers of functionality that explore different trade-offs between direct access to the underlying logic engine and user-friendly support for spreadsheets users.