Show AllOccurs when you specify an intersection of two areas that do not intersect. The intersection operator is a space between references.
Click the cell that displays the error, click the button that appears 
, and then click Trace Error if it appears.
Review the possible causes and solutions.
Using an incorrect range operator
To refer to a contiguous range of cells, use a colon (:) to separate the reference to the first cell in the range from the reference to the last cell in the range. For example, SUM(A1:A10) refers to the range from cell A1 to cell A10 inclusive.
To refer to two areas that don't intersect, use the union operator, the comma (,). For example, if the formula sums two ranges, make sure a comma separates the two ranges (SUM(A1:A10,C1:C10)).
Change the reference so that it intersects.
When you enter or edit a formula, cell references and the borders around the corresponding cells are color-coded.
Color-coded cell references
If there are no squares at each corner of the color-coded border, then the reference is to a named range.
Change references that are not to a named range
Double-click the cell that contains the formula you want to change. Microsoft Excel highlights each cell or range of cells with a different color.
Do one of the following:
To move a cell or range reference to a different cell or range, drag the color-coded border of the cell or range to the new cell or range.
To include more or fewer cells in a reference, drag a corner of the border.
In the formula, select the reference, and type a new one.
Press ENTER.
Change references that are to a named range
Do one of the following:
Select the range of cells that contains formulas in which you want to replace references with names.
Select a single cell to change the references to names in all formulas on the worksheet.
On the Insert menu, point to Name, and then click Apply.
In the Apply names box, click one or more names.