This message appears when the Polymorphic Spreadsheet Interpreter first analyzes the formulas in your model after you click the Solve button or the Check Model button in the Solver Model dialog.  Address is the worksheet address of the cell (in Sheet1!$A$1 form) where the error was encountered, and Error condition is one of the following:

OLE error Missing (
Invalid token Missing )
Unexpected end of formula Wrong number of parameters
Invalid array Type mismatch
Invalid number Code segment overflow
Invalid fraction Expression too long
Invalid exponent Symbol table full
Too many digits Circular reference
Real constant out of range External name
Integer constant out of range Multi-area not supported
Invalid expression Non-smooth function
Undefined identifier Unknown function
Range failure Loss of significance

Many of these messages will never appear as long as you entered your formulas in the normal way through Microsoft Excel, because Excel “validates” your formulas and displays its own error messages as soon as you complete formula entry.  Some of the messages you may encounter are described in the following paragraphs.

Undefined identifier appears if you’ve used a name or identifier (instead of a cell reference such as A1) in a formula, and that name was not defined using the Insert Name Define… or Insert Name Create… commands in Excel, this message will appear.  The “labels in formulas” feature was dropped in Excel 2007, and the Interpreter does not support this use of labels in formulas.  You should define these labels with the Insert Name Define… or Insert Name Create… commands, or else set Solve With = Excel Interpreter to avoid using the PSI Interpreter.

Circular reference appears if Excel has already warned you about a circular reference in your formulas, and it can also appear if you’ve used formulas in a “potentially circular” way.  (For example, if cells A1:A2 contain {=1+B1:B4} and cells B3:B4 contain {=1+A1:A4}, Excel doesn’t consider this a circular reference, but the PSI Interpreter does.)  If you must use circular references in your model, in the Platform tab of the Task Pane, change the Interpreter option from “Automatic” to “Excel Interpreter” so you avoid using the PSI Interpreter.

External name appears if your formulas use references to cells in other workbooks (not just other worksheets), and the Interpreter is unable to open those workbooks.  You should ensure that the external workbooks are in the same folder as the Solver workbook, or for better performance, move or copy the worksheets you need into the workbook containing the Solver model.

Multi-area not supported or Missing ) appears if your formulas or defined names use multiple selections such as (A1:A5,C1:H1).  While the Interpreter does accept argument lists consisting of single selections, such as =SUM(A1:A5,C1:H1), it does not accept multiple selections for defined names, or for single arguments such as =SUMSQ((A1:A5,C1:H1), (B1:B5,C2:H2)).  If you must use such multiple selections, you’ll have to set Solve With = Excel Interpreter.

Note:  As mentioned above, in the standard Excel Solver, result code 12 was associated with the message “Another Excel instance is using SOLVER32.DLL. Try again later,” which does not occur in modern versions of Excel and Window.