I'm confused - why do you want to dig it up? Are you moving it to a new position, so are you really asking, when is it alright to move it? And which Viburnum is it - evergreen one or not?

hi Garry and welcome to GoY.
Depends on which one it is.
if it is the one that flowers now I would leave it until late spring early summer.
If it is a summer flowering one then move it now.
If you are moving it now, lift it with as much of a rootball plus soil as you can manage. plant into its new home with plenty of compost to help it , firm it in well to stop it rocking in the winds. depending on its size you might want to reduce the size by half to help it settle. water it well and keep an eye on it .

hope this helps. if not ask further questions under this one.