SQL or Excel

The data below is from an Oracle table. I want to get the right date_req for each group of rcvr. The following is the conditions,

If calc is a decimal number, use the corresponding date_req
If the above condition is false then check calc for "1" and get the maximum date_req
Calc is qty_rec divided by qty_ord.  Possible value for calc is 0, 1 and a decimal number.
There can only be one decimal number (if exist) for each group of rcvr.

The last 2 line below is the result we need. Using SQL is the prefer method. Although, we can use Excel solution as a last resort. Appreciate the help.

rcvr      date_req      qty_ord      qty_rec      calc
a      1/1/2008      10      10      1
a      2/1/2008      20      5      0.25
a      4/1/2008      25      0      0
a      6/1/2008      30      0      0
b      7/1/2008      5      5      1
b      8/1/2008      10      10      1
b      1/1/2009      15      15      1
b      3/1/2009      20      0      0
b      4/1/2009      25      0      0
b      6/1/2009      30      0      0
b      7/1/2009      35      0      0
b      9/1/2009      40      0      0

Results
a      2/1/2008      20      5      0.25
b      1/1/2009      15      15      1