Create Dynamic List Property for Combobox - Exclude Certain Values from List

I would like to create a list source for my combobox based on the values in column A of worksheet ws_rstr.

As of now, what is working satisfactorily is :

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I need to enhance this to :

a) recognize when the reference database expands with the addition of new rows. A3 will always be the start, but column A may grow beyond the static row 37.
b) the data in column A may contains one or more values = 0. I do not want these included in the list source for the combobox.

Is anyone able to assist me with this?

OK, thanks dflak for your guidance!

In name manager, I created a named range (employeenumber) with a reference based on this forumla:

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where column A of worksheet "roster" hosts the employee numbers intended to populate the combobox of the userform. The data starts at cell A3, (A1, A2 are headers).

I am populating the contents of the combobox with this code (as part of the userform initialize code)that steps through the named range (employeenumber) extracting all the values with the exception of those = 0.

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I'm not able to determine if this approach is working as the code breaks with the line highlighted in red with an "Unspecified error".

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???