Is this a single value check box format?
If so, Replace Field contents can be used after doing a show all records.
If there are multiple check boxes and you want to set one box without altering the selected values in other boxes, Replace Field Contents can still be used, but you need a calculation that appends the needed value without deleting other values and without creating duplicate values in the field.
Oh My, THANK YOU! You have saved me about a millions hours of tedious work! Exactly what I was looking for! I really appreciate the quick and very helpful answer! I have been doing this the wrong way for ages!! Blessings,