Generate single drop down from items in four columns

Hi all,

I have a database in which each row contains data on a particular event. Column F to I have keywords relating to that event. For examply, F2 will have one keyword, G2 will have one and so on till I2. Some rows will not have all the keywords, maybe only two or three so some cells will be empty. Although the events are unique, the keywords will repeat themselves in more than one row. So one keyword can apply to many events. What I want to do is, in a user form, generate a single drop down list based on all the entries in column F to I and when the user selects a keyword, on a separate sheet display all the entries relating to that keyword. The database is in sheet called "Log Sheet", The search result has to be displayed on "Follow up".
Thanks.

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