Update Query

Hello,I am sure this is easy
I have an update query in my vb app.now I nees to include a where clause .if the len of the field is less then 14 spaces.
DBCommand.CommandText = " Update Table Set InternalControlNumber = '0' & InternalControlNumber "
this is my query I am not sure of the right syntax fro the where clause
Thank you

Here's the syntax as I'm not sure your original code makes sense

Update tablename Set x = y Where a = b