Help please with SQL query for getting next record value in previous row

hi.

i have this table for example:


and this SQL query:

prcrSql = "SELECT scaleqty, fld01, dim2, dim1, prcrule, finaldate FROM prcrdata WHERE finaldate>=getDate()-1 AND (dim1=30 OR dim1=40) ORDER BY dim2"

prcrRS.Open prcrSql


WHILE NOT prcrRS.EOF

insPRCR = "INSERT INTO prcr (mtrl,ofprice,minqty,maxqty,client,prcrule,fdate) VALUES ('"&prcrRS("dim2")&"','"&prcrRS("fld01")&"','"&prcrRS("minqty")&"','"&prcrRS("maxqty")&"','"&prcrRS("dim1")&"','"&prcrRS("prcrule")&"','"&prcr("prdate")&"')"
myCon.Execute insPRCR

prcrRS.MoveNext
WEND

Code (markup):

in the table above (image table) i have only the minqty (minimum quantity) and i want to set the maxqty (maximum quantity) 1 less than minqty of the next record.
for example at row 1: 4 (5-1)
at row 2: 7 (8-1)
and so on...

i want this result:


how i can do this with SQL or classic ASP or PHP;

thanks in advance.