Lowest multiple of $n$ over a certain threshold, $y$.

I'm looking for an equation to calculate the lowest multiple of any value $n$ greater than or equal to a given threshold, $y$. I've come up with a solution that works, but it's rather ugly and not incredibly efficient. I'll be using this within software, so efficiency matters to some degree.

Here's what I've come up with:
$x$ = $y$ (mod $n$) and $1$ x = 0 if y (mod n) = 0, otherwise 1
$m$ = $x(n(floor(y/n)+1)-y)+y$

This only needs to work for positive values of $y$ and $n$. Any suggestions would be greatly appreciated.

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Use the ceil function (not floor). –  dtldarek Mar 14 '12 at 16:16
It's $n\cdot\lceil y/n \rceil$.
If for some reason your programming system has only floor ($\lfloor x\rfloor$) and not ceiling ($\lceil x \rceil$) you can synthesize ceiling as if (x == floor(x)) then x else 1+floor(x). –  MJD Mar 14 '12 at 16:25