That would work... EXCEPT that the secondary Gross cells by default have the
formula to subtract contents of Shrink from Gross to arrive at an Estimated
Secondary gross.  So until a secondary gross, or both a Gross AND tare weight
are entered, Secondary Gross is Null.  Forgot to include.  If No secondary
Gross is entered, the Estimated Shrink is calculated from the NET Weight (
Gross - Tare).

So right now, I have 2 spreadsheet setup files... One for when the scale at
the plant is working, and a second that figures strictly an estimated shrink
as long as the trucks need to be weighed elsewhere.

  a             b                  C          D           E
Gross  Secondary    Tare        Net       Shrink

Default cell contents

A  Blank
B   Formula to give estimated secondary gross    =A2-E2
C   Blank
D   Formula (assuming in row 2)  =A2 -C2
E.  on sheet for estimated shrink    =D2 * .005

Ideally, the formula for shrink should determine if secondary Gross still
has the default formula or user entered number since THAT would determine how
to calculate Shrink

If Secondary Gross is user-entered, Shrink should be Gross - Secondary Gross
(=A2-B2)
If Secondary Gross still contains default formula, Shrink should use
Estimate (=D2*.005)

If nothing else, if you know how to do this with a user defined VBA function
that could be used in the spreadsheet, tell me.

I already programmed the spreadsheet setup in VBA so to set up the sheet,
the user only has to know the lot number, farm name, how many loads, and the
catch count, and the VBA coding will set up the spreadsheet with properly
placed total lines, grand totals, and correctly format the shift related
summary page of the spreadsheet.  So I'm by no means afraid to do this with
an added in VBA coded spreadsheet function to test whether B2 contains a
Formula.