Excel 2007 : How to make two VB codes work in harmony?

I am fairly new to VB and don't know how to code in VB. I want to accomplish multiple selection from a dropdown list in Excel and also add items in the dropdown list by entering them in the dropdown menu cell. I have the following independent codes to accomplish this:

Code for multiple selection code -

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Code for adding items in the dropdown menu by typing them in the cell -

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When I paste both these codes after opening "View Code" for a Workbook (Thisworkbook), I am not able to run the data validation list on that sheet as it results into compilation errors. How can I edit the codes to have the functionality I intend to achieve? Even better, could someone help me figure out a way for using these codes for the whole workbook instead of pasting them for each worksheet, as I have 40 worksheets and many workbooks? I have my list on another sheet (Sheet2) and the dropdown menu is on Sheet1 in cell A1. I am a newbie, so I would greatly appreciate detailed instructions. Thank you.

Edit: I have made changes in the code in "ThisWorkbook" to merge the code.