Index / Match to find next instance of a value

Hi,
I have a sheet which uses a search function. When a value is entered in to the "Search" sheet in C4, the formula in C9 is:

=INDEX(STS!A:A,MATCH(C4,STS!C:C,0))

which works fine.
the thing is, there could be more than one instance of the value in C4 and I want to get the next instance and put this formula into C11 and again into C13 for the next instance.
Can anyone help please?