NAME:
    calval
 PURPOSE: (one line)
    Validate overscan, cropping region, and calibration file settings.
 DESCRIPTION:

 CATEGORY:
  CCD data processing
 CALLING SEQUENCE:
    calval, isize, csize, mlow, mhigh, errflg
 INPUTS:
    isize  : Image size.
    csize  : Calibration file size.
    mlow   : Starting subscript in image.
    nhigh  : Ending subscript in image.
 OPTIONAL INPUT PARAMETERS:

 KEYWORD PARAMETERS:
    BANNER    : Banner line printed with error report (if SILENT=0).
    CSIZELAB  : Label for csize parameter, if error condition is printed.
    MLOWLAB   : Label for mlowlab parameter, if error condition is printed.
    MHIGHLAB  : Label for mhighlab parameter, if error condition is printed.
    DELTAMLAB : Label for deltamlab parameter, if error condition is printed.
    SILENT    : If set, No error report is generated.
    ISIZELAB  : Label for isize parameter, if error condition is printed.
 OUTPUTS:

 COMMON BLOCKS:

 SIDE EFFECTS:

 RESTRICTIONS:

 PROCEDURE:

 MODIFICATION HISTORY:
    Written by Doug Loucks, Lowell Observatory, April, 1994.