how to edit these macro for multiple select listings in data validation?

[pejoi]

hi guys,
i had a problem on a macro that can be used to select multiple listings in a column.the problem occurs when i make another data validation on a different column,it appeared the multiple listings.how to prevent a column to repeating inserting multiple listings? i had attached the worksheet.info ahad's sheet: b23 (column with multiple-listings),b45(i wanna this column to be single-listing).Please help me to rectify the problem.thanks.

macro:
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