Create a range of data that contains the list of valid choice for
column A and the valid values of B for each A. That is, something like

a 1 2 3 4
b 11 22 33 44
c 111 222 333 444

where a, b, and c are the valid values for column A and the number to
the right of each of those are the valid values for column B. So, for
example, if A1 = b, then the only valid values for B1 are 11, 22, 33
or 44. In validation custom formula, use something like

=NOT(ISERROR(MATCH(B1,OFFSET($E$1,MATCH(A1,$E$1:$E $4,0)-1,1,1,4),0)))

Here, change $E$1:$E$4 to the column in the above table that contains
the valid values for A1 (e.g, the cells containing the a, b, and c
values), and change the 4 at the end of the OFFSET function to the
number of values that are allowed (e.g., 4 = 11, 22, 33, 44 valid
values).

Cordially,
Chip Pearson
Microsoft Most Valuable Professional,
Excel, 1998 - 2010
Pearson Software Consulting, LLC
www.cpearson.com




On Tue, 30 Mar 2010 10:58:02 -0700, WT
wrote:

I have a situation that I hope you can help me with or at least point me in
the right direction.
I have a spread sheet where column "A" has a defind set of values
{A,B,C,D,E} and that cell has a validation set so that only those value can
be entered. Based on the entry in column A, I need to force an entry in
Column B but allow the user to enter from another set of selections
depending on the value in column A.
example:
A1 = A B1= set(F,G,H,J)
A2 = C B2= set(K,L,M,N)
Also I would like to force the user to make the entry in column "B" before
they can proceed to the next row.
Any ideas???