Upper and lower value in Inspection Plan

Hi,

I have one characteristic CT1 having no lower or upper range. I have created one Master Inspection characteristics as MIC1 with reference to CT1, so does not have any values. Now CReating one Inspection PLan IP1 ( t code QP01) with MIC1. By default there is no values are there and tried to maintain the lower and upper limit by unloacking the characteristics. But still greyed out.

Is there any way to maintain range in inspection plan in this situation?

Thanks

krish