how to change list of empty cells with a value ?

[Excel2003] If is not so easy to input repeated value to a different cell location.
And so much moving cursor and pasting to do the job! Is there any solution ?

if this is the selection of cells, and "-" means empty, new value to be replace = "x
"
a
-
-
b
c
-

becomes

a
x
x
b
c
x

how to code it using the current region to replace current empty cell with "x" ?

thanks for helping hands! I really need this to speed up my work!