The combination "uX" (editable read-only, with validation) now causes an automatic exit with EXITCODE -48 whenever the cell is ENTERED (rather than EXITED).
This makes some sense, given that you should not be able to modify the cell if it is read-only, so there isn't any point in post validation. But there is a point in pre-validation if you wanted to perform some action whenever the user selects one of these cells, either by clicking on it or using keyboard navigation.) In this mode, it does not exit for validation on attempts to key in data (as it does for a read-only editable cell without the X code).
Note that the xtr'xvalidate flag will be set to +2 to indicate that pre-validation of the cell identified by xtr'targetrow and xtr'targetcol is needed.
