Penetration Testing: sql injection with order by

[dietf dietf <dietf () yahoo com>]

Hi all,
I am trying to make an injection with the statement below,

SQL = "SELECT ProID, CusID, Name FROM ProTur WHERE Lan=0 AND CusID='%Customer%' ORDER BY Sira, ProjeTurID"

in the statement above I inject ")select @@version-- for the variable Customer. But unless I have ended inject code 
with -- nothing happens.
I get
SQL = "SELECT ProID, CusID, Name FROM ProTur WHERE Lan=0 AND FirmaID=")select @@version-- ORDER BY Sira, ProjeTurID"
what is the problem? can anybody tell me?
Is the problem occurs from the word ORDER BY?
Thanks