To do so add the following code to BeforeAdd/BeforeEdit events (C#):
foreach(var field in values.ToList())
{
values[field.Key] = field.Value.ToString().ToUpper();
}
return true;
If you also want all text to appear in upper case as it being entered add the following to 'Custom CSS' section in Style Editor.
.rnr-control input, .rnr-control select, .rnr-control textarea
{ text-transform: uppercase; }