VBA to move a cell to next blank cell

I have a task to consolidate all figures into one column.

I need to create a Macro to move negative values in column C ( any column as I select) and paste the same value to left empty cell.

Before

      A   B     C     D    E   F
1         10   
2              -18
3              -12
4              -14
5         19
6         20
7
8

After
      A   B     C     D    E   F
1         10   
2         -18
3         -2
4         -14
5         19
6         20
7
8

Thanks