Just reverse the subtraction:

=IF(B4="","",B4-B3)

Hope this helps.

Pete

On Dec 17, 6:37*pm, Scoober wrote:
Hi,

How can I make this formula show as a negative figure when it shows weight
has been lost and positive when weight has been put on. At the moment it is
doing the opposite to what I require.

b3 = last weeks weight
b4 = This weeks weight
c4 = answer

=IF(B4="","",B3-B4)

Thanks in advance.

Scoober