There's a sample file here that may help you:

http://www.contextures.com/excelfiles.html

Under Data Validation, look for 'Limit Data Validation Selection'

jrrbama wrote:
My scenario is below. I have three columns of dependent validation.

1. Select a value from dropdown list in A1. €“ O.K.
2. Dropdown list in B1 becomes dependent on selected value in A1. €“ O.K.
3. Select a value from list in B1. €“ O.K.
4. When there is a value in B1, A1 list is reduced to the single value
which was selected in step 1. €“ O.K.
5. Dropdown list in C1 becomes dependent on selected value in B1. €“ O.K.
6. Select a value from list in C1. €“ O.K.
7. When there is a value in C1, I need the same to occur here as in step 4,
B1 list is reduced to the single value which was selected in step 3.

The validation code for the dropdown cells is:

A1 - =IF(B1="",AList,INDEX(AColumn,MATCH(A1,AColumn,0)) )

B1- =OFFSET(AStart,MATCH(A1,AColumn,0)-1,1,COUNTIF(AColumn,A1),1)

C1- =OFFSET(BStart,MATCH(B1,BColumn,0)-1,1,COUNTIF(BColumn,B1),1)




--
Debra Dalgleish
Contextures
http://www.contextures.com/tiptech.html