Template:CheckNumber

The template is used for validating inputs into forms and takes the following 2 parameters:

1. Any previous error message
2. The field to be checked

and checks if parameter 2 is a number. It returns an error message if it does not, referring to the field 'First page'.
This template is currenly not used. The suggestion in the error message to place page numbers like "S12-S15" into the volume field does not solve sorting problems.