You say "sometimes": so "sometimes" you know Gross and need Net and other
times known Net and need Gross.
Suppose A2 has gross as number, B2:E2 have formulas such as =A2*10%, and F2
has =A2-SUM(B2:E2)
In place of just experimenting with A2 to get a know Net, use Goal Seek to
get the know F2 by varying A2
Does this address the question?
happy new year

Hi, Vinnie.  I am not an accountant and don't know how withholding works,
but my understanding is that withholding changes based on how much you
actually make for the calendar year.  If that's true, I believe you need a
column or worksheet that keeps a running total of that person's pay so that
when they cross an appropriate threshold, they are bumped to another tax
bracket.

I would personally set up a tax table on Sheet2 that has all the breakpoints
for different taxation levels (if I recall, FICA, Medicare, Federal, and
State all have separate thresholds independent of each other that dictate
how much to withhold and when to start and stop withholding for that
particular tax).  Once you set up your table with 2006 data, you'll easily
be able to update it with 2007 and future years' changes.

Then I'd go back to Sheet1 and set up 3 data entry columns: column A for
name or ID, column B for the Wage Entry, column C for the word "Net" or
"Gross".  Set up the worksheet data and formulas as a list (give the list a
name) and start putting in your formulas.  Finally, I'd set up yet another
worksheet to track each person's YTD gross pay (you could also use it to
track your totals for the other columns to make it easier to complete your
W2s in January).

Does that help?

Hi.  If b,c,d & e represent different percentages of Gross, then I believe
the equation is:

Gross = Net/(1 - b - c - d - e)