I do not know much about VBA, but if I were you I would use the combination of Data validation and offset.
Let say your list that is going to grow is in column A, and you want your picklist in C5.
First in a cell of your choice create a an offset formula as such( this optional, I always do this to see the hints to create an offset you can simply type the formula directly into the source box of the data validation):
=OFFSET(A2,,,COUNTA(A:A)-1,), the "-1" is for counting for table header, if you do not have a header then ignore -1.
then copy the formula , goto cell C5, select data validation, select list, and in the source box paste the formula. as you add names to the list the pick list gets updated accordingly.