Variable Data Validation Range in a Macro

[elotromateo]

I'm trying to add a list to a cell with a macro. I am using a list of cells as the options for the list in the target cell. Unfortunately, this list is going to change in length and I can't figure out how to add a range for this kind of setup. I know the location of the first cell (RowStart), and I can search for the last cell in the macro (RowEnd), but I can't put them in after "Formula1:=". How do I add the range into this?

Sub UpdateBldgs()


Set RowStart = Worksheets("Update Sheet").Cells(3, 12)
Set RowEnd = Worksheets("Update Sheet").Cells(Range("L" & Rows.Count).End(xlUp).Row, 12)
x = RowStart.Address()
y = RowEnd.Address()

Range("C1").Select
    With Selection.Validation
        .Delete
        .Add Type:=xlValidateList, AlertStyle:=xlValidAlertStop, Operator:= _
        xlBetween, Formula1:= ?
        .IgnoreBlank = True
        .InCellDropdown = True
        .InputTitle = ""
        .ErrorTitle = ""
        .InputMessage = ""
        .ErrorMessage = ""
        .ShowInput = True
        .ShowError = True
    End With

 

[elotromateo]

A follow-up of sorts. I figured out that I can cheat and just add the entire column and the list will only show those cells that are not blank. Unfortunately, I also need to do this for a Combo box, but this shows the blank cells, so I can't sneak out of this one. Now I don't know what to put after ".ListFillRange =".

Sub Macro7()
'
x = Range(Cells(3, 12), Cells(Range("L" & Rows.Count).End(xlUp).Row, 12))

    ActiveSheet.Shapes("Drop Down 7").Select
    With Selection
        .ListFillRange = ?
        .LinkedCell = "$G$6"
        .DropDownLines = 8
        .Display3DShading = False
    End With
End Sub