Can Varbinary And Varchar Lengths Be Declared Dynamically?

I just learned that bit masking a varbinary column can increase it's length in bytes unnecessarily. For example, I ran the following...

declare @v1 varbinary(max)

set @v1 = 0x0100AB

select len(@v1)

set @v1 = @v1 | (len(@v1) - 2) * 256

select master.dbo.fn_varbintohexstr(@v1)

select len(@v1)
...and get
3
0x00000000000101ab
8

This messes up a plan I had for varbinary column use.

So I quickly tried the following to look for strategies to deal with this unwanted growth...thought being that while I'm passed a varbinary(max), operating on a varbinary that matches its passed length would avoid the unwanted growth after bit masking....


declare @i int

set @i = 5

declare @v2 varbinary(@i)

...but got errors.

So I suppose I can use a combo of the len, substring etc functions to correct the situation after bit masking but would like to know if the more elegant approach of dynamically sizing a varbinary is possible in t-sql, or if perhaps there is a way to prevent the unwanted growth during bit masking.