Looking for a formula to compare weight loss or gain tracked through 3 cells

[FIFTYFINGERS]

Hi All;
i am trying to track weight loss or gain by entering different weights in cells L2(starting WT) Q2(next WT) and W2(final WT) with the formula in AU2.
Here is an example of formula i used: =IF(W2="","",W2-$L2)
My problem is, if i don't enter a weight in W2 the nothing appears in AU2.
It works if i put a weight in W2.

[Miraun]

Not sure what the ask is... You described an example, you gave an equation, and the expected result based on that equation...
If you're looking for something that will calculate Q2 if W2 is blank, you can use:
=IF(W2="",Q2-L2,W2-$L2)

[FIFTYFINGERS]

Thanks the formula you sent worked