This is a great example of when using the Group Concatenation function is helpful.  You're quite right that it's easy to identify customers who did business with you more than 2 months ago but you need to see only those who did business more than 2 months ago and haven't done business with you since.

The following example shows an Opportunity report and uses the Close Date as the date to identify when the business was conducted.  However, you could build a similar report based on Customer Orders or Invoices and use the document date to identify when the business was conducted.

Within an Opportunity report: 

• add a column for the customer's object reference (ie, their unique identifier), by clicking Add column from Opportunities > Prospective customer >

  Object Reference.

• add a column for the customer's name by clicking Add column from Opportunities > Prospective customer name.

• add a column called Recent and Old that looks at the Close Date of the Opportunity, works out whether it's more than 60 days ago and returns the word 'Old' for ones that were more than 60 days ago and 'Recent' for the ones with a Close Date within the last 60 days.  This column then concatenates (puts into one long string) all the results.  The formula used for this is:

GROUP_CONCAT(IF(DATEDIFF(CURDATE(), close_date) >60, 'Old', 'Recent') SEPARATOR ', ')

You don't have to use the SEPARATOR ', ' part if you don't want to - it's there to create a comma and a space between each entry in the string so it's easier on the eye.

• Summarise the report so it shows one row for each customer by opening the Summarise by tab, clicking Add summary column and choosing Prospective customer's object reference.

At this point your report should look something like the one shown below (click to enlarge).

Notice that the row for ORG-1 (Osiris Corporation) shows two entries of Old, meaning that there are two Opportunities for them each of which has a Close Date that is more than 60 days ago.  The rows for ORG-7 (Addvantage Media) and ORG-61 (ABC Company) have both Recent and Old Opportunities.  It's rows like this that you want to exclude from the report because, although these companies did business with you more than 60 days ago, they have also done business more recently.  To do this: 

• Open the Criteria tab, click Add calculated criteria and choose Recent and Old.  Within the Operator field choose does not contain and in the Text field type Recent.

You should now have a report that shows one line item for each company who hasn't done business with you recently.

NOTE:  Within an Opportunity report you'll want to apply criteria to limit the results to only those Opportunities that have been won, rather than ones in the pipeline or that were lost.  If you use an Order or Invoice report, this won't be necessary.

In the next release of Workbooks, due out in late summer, you can build the same report by undertaking the following steps:

• Create a new blank report based on Opportunities. Within the Details view add a column for Prospective Customer Object Reference (Prospective Customer > Object Reference), Prospective Customer Name and Close Date.

The details view now shows a list of all Organisations with Opportunities and their Close Dates. A Summary View can be built to show only Organisations who you haven't done business with during the last 60 days. To do this:

• Select 'Add Summary View' and 'Add grouping column'. Group by 'Prospective Customer Object Reference'.
• Add a value column for 'Prospective Customer Name'.
• Add a Calculated column which uses the following formula:

                     'GROUP_CONCAT(IF(DATEDIFF(CURDATE(),  PARENT('Close Date')) >60, 'Old', 'Recent') SEPARATOR ', ')'

This formula looks at the Close Date of Opportunities and works out whether it's more than 60 days ago and returns the word 'Old' for ones that were more than 60 days ago and 'Recent' for the ones with a Close Date within the last 60 days. This column then concatenates (puts into one long string) all the results.

• Add a Calculated criteria which says that 'Recent and Old does not contain Recent'.

You should now have a report that shows one line item for each company who hasn't done business with you recently.

NOTE: Remember that within an Opportunity report you'll want to apply criteria to limit the results to only those Opportunities that have been won, rather than ones in the pipeline or that were lost.  If you use an Order or Invoice report, this won't be necessary.