I have TblCase table with the following fields:
CaseNumber (duplicates ok), CompanyName, ProductName, and CaseSubNumber (duplicates ok).

When a new ProductName (Ex: Aspirin) is ordered from CompanyName Bayer Co., a button New Case # is clicked to open New Case # form in which a new CaseNumber is automatically generated to the next highest number in the CaseNumber field. If this order is new then the first "CaseSubNumber" is set to 0 by default.
When more Aspirins are purchased from Bayer Co., another button New Case Sub # is clicked to open New Sub Case # form in which a new case sub-number is automatically generated to the next highest number in the CaseSubNumber field, however, related to the same CaseNumber field.

See Examples "TblCase" table would show:
- Case# 100, Product Name Aspirin, Company Name Bayer Co., Case Sub # 0
- Case# 100, Product Name Aspirin, Company Name Bayer Co., Case Sub # 1
- Case# 100, Product Name Aspirin, Company Name Bayer Co., Case Sub # 2
- Case# 101, Product Name Tylenol, Company Name McNeil Co., Case Sub # 0
- Case# 101, Product Name Tylenol, Company Name McNeil Co., Case Sub # 1
- Etc.

thanks for any help.