You might try doing some print and help statements on your variables right before you call the ROI_THRESH_DOIT to make sure you are passing what you think you are passing. I was able to use 'dmin' and 'dmax' from ENVI_STATS_DOIT to create some ROIs so I don't think there is anything wrong with using a variable. Perhaps you can copy your code example here so we can see what might be going wrong. Or you can contact Exelis VIS technical support directly with this question.

I have done what you told me and, as far as I know, the variables are being correctly passed. My code is simply: envi_open_file, mod_file, r_fid=image_fid envi_file_query, image_fid, dims=imagedims ENVI_DOIT, 'ENVI_STATS_DOIT', CANCEL=cancel, COMP_FLAG=0, FID=image_fid, DIMS=imagedims, $ POS=0, DMIN=datamin, DMAX=datamax ENVI_DOIT, 'ROI_THRESH_DOIT', /NO_QUERY, DIMS=imagedims, FID=image_fid, POS=0, $ MIN_THRESH=datamin, MAX_THRESH=datamax, ROI_ID=ROI_fid, ROI_NAME='adan', ROI_COLOR=1 The ENVI window appears, the process of ROI creation reaches 100%, and the ENVI window disappear. But then the program stops with an error, and ROI_fid is "undefined"; however, the value of datamin is "-53.0000" and datamax equals 152.000