Excel copy formula???

Occasional Visitor
Hey everyone,

Really hoping someone could help me out with this formula I've been trying to work out for the last week but just can't do it.

I'm trying to copy a input on sheet2 C3 to sheet1 C3 and have it check if there is already an input in sheet1C3 then place it to sheet1 C4 and repeating this process over and over,

Also if the first input on sheet2 is cleared then the copy on sheet1 STAYS and does not clear...

Thank you