excel - Declare cells or range as variant in VBA

It would be very basic question.

I want to declare cells as variant, to
substitute repeated typing,
like

a =
cells(1,1)
or
a =
range("a1")

then

a.select or
a.value,
etc..

but error occur with

runtime
424

I want to
understand what is problem, and how can i
do.

Thanks,