You say "Any time  the current  cell changes ...". Do you mean that the
contents of the current cell  changes, or do you mean that you move the
selection to a different cell?

I'll assume that you are talking about changing the selection.

If so, you need code - not formulas. You will need to use the "worksheet
selection change" event. That event has a parameter which is the cell that
is the current selection.

Best way is to use the Intersect function to see if there is an intersection
between the current cell and a Range function call containing a
comma-separated list of your various small ranges.

If there is an intersection, then you know it's one of your wanted cells.
Simply assign the value of the active cell into the value property of M7.
Otherwise, assign an empty string.

A few Google searches will get you appropriate examples.

Note that this will only work  when the selection changes. I.e. it will not
work for the initial position of the active cell.