Please help:

I have an Excel 2007 formula problem. I think the problem that I have
requires an IF function and I've been trying to put it together but it's a 7
part formula and they keep canceling each other out somehow. I have several
scenarios that I'd like to create in one formula for one cell: it goes like
this:

D1 should be the result of:

Part 1: If A1 has a numerical value entered, and B1 is blank and C1 is Blank
then D1 should Display 1 (I got this
far:=IF(A1<"",1,""*AND(B1="",1,""*AND(C1="",1,"") )))
Part 2: If A1 is blank, B1 has a numerical value and C1 is blank the D1
should display 2
Part 3: If A1 is blank, and B1 is blank but C1 has a numerical value then D1
should display 3.
Part 4: If A1 has a numerical value and B1 has a numerical value but C1 is
blank then D1 should display 4
Part 5: If A1 has a numerical value, but B1 is blank and C1 has a numerical
value then D1 should display 5
Part 6: If A1 is blank but B1 and C1 each have a numerical value then D1
should display 6
Part 7: If A1, B1, and C1 each have a numerical value in their cells then D1
should display 7.

That's all of it. I would really appreciate the help. Thanks in advance.