I often get a circular reference message from Excel. Does this mean I’ve made an error?
How can I resolve circular references?
When Microsoft Office Excel displays a message that your workbook contains a circular reference, it means there is a "loop," or dependency, between two or more cells in a worksheet. For example, a circular reference occurs if the value in cell A1 influences the value in C2, the value in cell C2 influences the value in cell D2, and the value in cell D2 influences the value in cell A1. Figure 10-1 illustrates the pattern of a circular reference.
Figure 10-1. A loop causing a circular reference ...