Again thank you so much . Am enjoying this.  Sorry for length of queries but am trying to sort this database asap. 1.  When I started with a data base of medical results, ( with access 2000) I battled with the number and decimal value fields.I was eventually advised to set all as currency as there was no problem in enterring the decimals or doing calculations. Is this still  acceptable.Have used this format with the new database.
2. Null values. I was advised to use a default value by a statistician to have a default value that equated to " no data available"    I set this as -9 as the database at that time set 0 automatically as default and I used 0 as a value and occasionally used '-' values up to -3. Is this still acceptable or is it now possible to use null value in number fields that will be used for calculations. I understand from what you have just said that I may be able to replace the -9 with a blank value with a query later on. Thank you so much again excellent series

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Reply from Richard Rost:

1. Use currency for DOLLAR values. Otherwise use doubles for floating point numbers or long integers for everything else... when in doubt.

2. I would use NULL for "has no value." You can replace all of your negative numbers with an UPDATE QUERY.