Hide cell

I am trying to create a template where y=the data is formated similar to a group sort display.
eg
1 a
1 b
1 c
2 a
2 b
2 c

formated to
1 a
b
c
2 a
b
c

I am currently doing this by If(a2=a1,"",a2)
in which case I lose the value that was origionally there. Is there a hide cell command that could be used? Eg If(a2=a1,do not display,display)?

regard
Mike