Assume that you have an Excel 2010 worksheet that has the Sheet.EnableFormatConditionsCalculation property disabled. When you change a cell that uses conditional formatting in the worksheet, the conditional formatting is not applied immediately to the cell.
To resolve this issue, apply the following hotfix:
2597142 Description of the Excel 2010 hotfix package (x86 Excel-x-none.msp, x64 Excel-x-none.msp): February 28, 2012
Registry key information
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 How to back up and restore the registry in Windows
After you install the hotfix package, follow these steps to enable the hotfix:
Click Start, click Run, type regedit in the Open box, and then click OK.
Locate and then select the following registry subkey:
On the Edit menu, point to New, and then click DWORD (32-bit) Value.
Type IgnoreEnableFormatConditionsCalculationOnLoad, and then press ENTER.
In the Details pane, right-click IgnoreEnableFormatConditionsCalculationOnLoad, and then click Modify.
In the Value data box, type 1, and then click OK.
Exit Registry Editor.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.