setdef may specify a list of acceptable characters rather than complete field entries. To use this method, specify the { code and then load setdef with a string of the characters you want to accept. Note that any input characters must first pass the normal type code test and then must be in the setdef string, so you may wish to specify the A type code as well. For example:
setdef = " 123ABCabc+-"
This would limit input to the numbers 1, 2, and 3; the letters A, B, C, a, b, and c; the plus sign, minus sign, and space. Note that upper and lower case must be listed independently.
