IF forumals, Autofill?

I have some formatting I am trying to figure out.
11 November 2015 Heater Receiving.xlsx

Here is what I need:
Column I to stay blank until column H is filled in, but when any value is entered into column H, I need column G- column H to fill into column I

But I still need for the if functions (unless there is a better formula to input) for column K & L to stay working (currently K is True if column I & column F are ='s & Column L is true is Column H is 0)

I am still learning formulas & such & this ability would make life so much easier!

in I2

=IF(H2<>0,G2-H2,0)

in J2

=IF(I2<>0,I2-F2,0)

in K2

=IF(I2=F2,TRUE)

in L2

=IF(H2=0,TRUE)

This doesn't work for me. See it works assuming the H will not be =0. Column H can have any #, I only want it to subtract IF a # is entered into H. During the work time, H may not have a # entered (the current formula is =G1-H1 (at all times) which means column I always has a # in it, which throws our workers off, b/c there should show nothing received & it shows the correct qty received, even though nothing has been touched.

For example:
Column
F G H I J
Qty to Rec Release # to Start RL # Qty Finish # Received Difference
100 120 120

In this example we receive 100 peices, our Open PO is for 120 pc. As it stands, when they START receiving, column I (G1-H1)will show the full Qty in G b/c nothing is entered into H. However, nothing can be entered into H until they workers are DONE receiving. So I need for I to not apply the formula UNtil a number has been manually entered into Column H

It should look like this while in progress
Column
F G H I J
Qty to Rec Release # to Start RL # Qty Finish # Received Difference
100 120

& this when finished
Column
F G H I J
Qty to Rec Release # to Start RL # Qty Finish # Received Difference
100 120 20 100 0

If H2=0, then I2=0 (or you could set I2 to blank) which is what you asked for! I2 is only calculated when h2 is NOT 0. same for J2.

If you want cells to be blank, formulae need adjusting.