Count Blank Cells Only If A 1 Is Previous

getting a formula to do this

I have
......D E
5 )......1
6 )......2
7 )......3
8 )......4
9 )......5
10)......6
11)......7
etc down to 31

They only show up when the cell next to it is not empty.

=IF(ISBLANK(D5),"0",(1))
=IF(ISBLANK(D6),"0",(2))
etc

If nothing is put into say D5 D6 or D7 but something is put in D8 then i would like E8 to become 1 as it is the first to be filled.Then when D9 has something in it, it becomes 2 if D10 has nothing in it it gets left blank but when d11 has something in it e11 becomes 4 counting the blank cell in between.

How can this be done.