I see You already got your answer, but, wouldn't this work?

local laTotal(1)

laTotal[1] = 0
select SUM(JN6.nJN6_3) ... Into array laTotal

* If there were no records "tallied", laTotal would still be 0

LcMessage = "Amount of it is " + Transform(laTotal[1])

>In this command:
>
>SELECT SUM(JN6.nJN6_3) FROM FORCE JN6, JN5, JN2, JN1 WHERE JN6.nJN6_8 = JN5.nJN5_1 AND ;
>JN5.nJN5_2 = JN2.nJN2_1 AND JN2.nJN2_3 = JN1.nJN1_1 AND JN1.nJN1_1 = LnCurentCompany AND ;
>JN6.nJN6_1 = GnYear AND JN6.nJN6_2 = GnMount INTO ARRAY LaTemp
>LnTotal = IIF(EMPTY(_TALLY), 0, LaTemp(1))
>
>Variable LnTotal have a value as 0 because SUM(JN6.nJN6_3) is 0.
>
>I want to change type of LnTotal from Number to String by STR() function but value of ALLTRIM(STR(LnTotal)) is 0 (No "0") and I can not add it to a string. For example:
>LcMessage = "Amount of it is " + ALLTRIM(STR(LnTotal))
>Value of LcMessage is 0
>But when SET ENGINEBEHAVIOR 80 it works correct! And value of LcMessage is "Amount of it is 0"
>I can not change type of LnTotal and every variables that makes as LnTotal!
>I want to have SET ENGINEBEHAVIOR 90 but I can do this.
>Please help me.