Using Excel 2007

I would like to get a formula that will allow me to count entries in column
C, but if an entry is made in column D that would supersede what is in column
C.

When an entry is made into column H I would like the total for columns C or
D to reflect this i.e. total number counted should drop.

I have listed names at top of s/sheet and totals are to sit in H1, H2 etc.
Hope you can assist. Let me know if you require additional info.

Cheers,
Paul