Pop-up Excel Calendar 1.4.4 is a Office Suite product from office-kit.com, get 4 Stars SoftSea Rating, Pop-up Excel Calendar is an Excel COM add-in which, when installed, adds a pop-up calendar to your Excel. The pop-up calendar can be activated automatically or manually, allowing you to easily work with date values in Excel workbooks or templates - For example, to enter a date, you click a date cell, and pick a date from the calendar. Download the free and fully functional trial version to see how Pop-up Excel Calendar works for you.

Activate the Calendar Automatically
Pop-up Excel Calendar displays an in-cell icon button automatically when you click a cell which:

Has a date format. To set the format of a cell in Excel, right click the cell and choose Format Cells. On the Number tab choose Date in the Category list, and then choose a proper date format in the Type list.
Has a date value. For example, if a cell is formatted as "General" but has a date-like value "September 1 2006", Pop-up Excel Calendar will display the in-cell icon button when you click the cell.
Underneath a cell with a date value or format in it.
Underneath a cell that has some form of the word "date" in it
You can enable or disable the above options respectively in the Settings window.

Activate the Calendar Manually
If you want to enter a date value in a cell, but the in-cell icon button is not shown automatically when you click the cell, you can display the calendar manually by the following operations:

Click the Calendar! button on the Pop-up Excel Calendar toolbar (Excel 2000/XP/2003).

Click the Pop-up Calendar button on the Standard toolbar (Excel 2000/XP/2003).

Right click the cell and choose Pop-up Calendar (Excel 2000/XP/2003/2007).

Click the Calendar! button in the Pop-up Calendar group on the ribbon (Excel 2007).

(Click to enlarge)

In Excel 2000/XP/2003, if the Pop-up Excel Calendar toolbar is not visible, click Excel menu View -> Toolbars -> Pop-up Excel Calendar to display it. You can also choose to display or hide the button/command on the Standard toolbar and right-click menu with the Settings window, which can be opened by clicking the Settings button on the Pop-up Excel Calendar toolbar, or clicking the Settings button on the pop-up calendar window.

In Excel 2007, you can change the installation mode of the Pop-up Calendar ribbon group to be either in a separate tab or the standard Insert tab, by choosing the corresponding option located on the Settings window.
The license of this office software is Free Trial Software, the price is $19.50, you can free download and get a free trial before you buy. If you want to get a full or nolimited version of Pop-up Excel Calendar, you can buy this office software.