Hi @cchan000
Disable the submit button by setting displaymode property for button as
If(dateEnd.SelectedDate<dateStart.SelectedDate,DisplayMode.Disabled,DisplayMode.Edit)
Also add a label with erro message text
and set visible property of label to
dateEnd.SelectedDate<dateStart.SelectedDate
where dateStart and dateEnd are control names of date field
Regards,
Reza Dorrani
If this post helps, then please consider Accept it as the solution to help the other members find it more quickly