Here is an example of seting the limits in a translateY channel.

                translateY ytran
                        {
                        name GetStringRes(1028,13)
                        initValue -0.00309944
                        hidden 0
                        forceLimits 4
                        min -1.500
                        max 1.300
                        trackingScale 0.001
                        keys
                                {
                                static  0
                                k  0  0
                                }
                        interpStyleLocked 0
                        }

The relevent lines are "forceLimits 4", which instructs Poser to use limits for this channel, the next two lnes (min & min) that tell Poser what the limits are.