Background: I am making a chart where monthly expenses are represented by
vertical bars and the monthly budget is a constant, for the entire year,
which is represented by a horizontal line. If a vertical bar for a particular
month rises above the horizontal budget line then I have exceeded my budget
for that month.

What I can do: I can create this chart if I use a monthly budget row where
each cell in the row has the same value.

What I want to do: To keep my spreadsheet manageable, I want to have the
monthly budget specified by a single cell, rather than an entire row, because
it is a constant for the entire yerar.