Formula

=a*b*MONTH
Results in error if Named Range is picked up from a drop down box

eg: Jan set of values
Feb set of values

Putting named range in formula directly works fine.
Point to a cell called month where users select the appropriate month
yields errors

How do I get the range values passed correctly to the formula if the
drop down box is named MONTH?
Where Month = Drop Down
and Month is a named range

Workarounds??