Every time you perform a find, the value of get ( RecordNumber ) will change, so I don't see how you can use record numbers in a find to get what you want here. Just changing the sort order will change the record number here.
I'd set up a loop here and use Omit Records to omit all but the first 100 records. After sending the email, I'd use Replace Field Contents to set a value in a "mark" field so that I can repeat the find to pull up my original found set, but with criteria that uses the value in this "mark" field to omit the records already used to generate emails. When my find results in zero found records, all my records have been processed.
Thank you! I'll give that a try. If I have any problems I'll let you know. Thanks for your help!