Add data via userform to specific cells

Hello,

I am having trouble figuring out a code to add data to specific cells. Ultimately, I want to add data to a cell and then have it go down to the next cell and so on. Here is a snap shot of what I want to happen.

Selection
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cells
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*the number list is ComboBox5 and the Add button is Private Sub Add1_Click(). My range is ("month") which is Sheet12!$P$17:$P$28

The whole function is supposed to act as an advanced filter search. But I want the range I enter data in to be dynamic and so, I want to be able to add to the list.

hope that makes sense!

thank you very much in advance!