System.Diagnostics.Process[] excelProc = System.Diagnostics.Process.GetProcessesByName("EXCEL"); System.DateTime startTime = new DateTime(); int m, killId = 0; for (m = 0; m < excelProc.Length; m++) ...{ if (startTime < excelProc[m].StartTime) ...{ startTime = excelProc[m].StartTime; killId = m; } } if (excelProc[killId].HasExited == false) ...{ excelProc[killId].Kill(); }