[Zax]

OK, I finally solve my problem, with the following code (maybe it could be optimized):

function .executeCmd(cmdStr, isMacroBoolean, noPrintErrorBoolean) -- return "", or error string
    local cmdStr = cmdStr or ""
    local tbl = {strsplit("\n", cmdStr)}
    
    local function executeString(str) -- return "", or error string
        local str = str or ""
        local func, errorMessage = loadstring(str)
        if (not func) then
            return "slash command LUA error #59000."
        else
            local success, errorMessage = pcall(func)
            if (not success) then
                return "slash command error #59001."
            else
                return ""
            end
        end
    end
    
    local resultStr = ""
    for i, strLine in ipairs(tbl) do
        if (resultStr ~= "") then break end
        if (isMacroBoolean) then
            --------------------------- macro ("/" needed)
            if (string.sub(strLine, 1, 1) ~= "/") then strLine = "/"..strLine end
            if (string.sub(strLine, 1, 5) == "/run ") then
                strLine = string.sub(strLine, 6)
                resultStr = executeString(strLine)
            elseif (string.sub(strLine, 1, 8) == "/script ") then
                strLine = string.sub(strLine, 9)
                resultStr = executeString(strLine)
            else
                DEFAULT_CHAT_FRAME.editBox:SetText(strLine) -- sent to Chat Box
                ChatEdit_SendText(DEFAULT_CHAT_FRAME.editBox,0)
            end
        else
            --------------------------- command ("/" not valid)
            if (string.sub(strLine, 1, 1) == "/") then strLine = string.sub(strLine, 2) end -- delete char 1
            resultStr = executeString(strLine)
        end
    end
    
    if ((resultStr ~= "") and (not noPrintErrorBoolean)) then print(resultStr) end
    return resultStr
end