Приведенная выше формула требует знака минус в первой строке: "= IF (A1 <-999500000000" * </p>
=IF(A1<-999500000000,TEXT(A1,"#,##.#0,,,"" TB"""),
IF(A1<-9995000000,TEXT(A1,"#,##.#0,,,"" GB"""),
IF(A1<-9995000,TEXT(A1,"#,##0,,"" MB"""),
IF(A1<-9995,TEXT(A1,"#,##0,"" KB"""),
IF(A1<-1000,TEXT(A1,"#,##0"" B """),
IF(A1<0,TEXT(A1,"#,##0"" B """),
IF(A1<1000,TEXT(A1,"#,##0"" B """),
IF(A1<999500,TEXT(A1,"#,##0,"" KB"""),
IF(A1<999500000,TEXT(A1,"#,##0,,"" MB"""),
IF(A1<999500000000,TEXT(A1,"#,##.#0,,,"" GB"""),
TEXT(A1,"#,##.#0,,,,"" TB""")))))))))))