Put the data validation on the cells where the values are entered. For
example, if the 1,2,3 are in cell A1:A3, and the total is in A4:

Select A1:A3
Choose DataValidation
For Allow, choose Custom
In the formula box enter: =$A$3=6
Click OK

Danny wrote:
I would like to know if it is possible to use data validation on a
field that is summing/totalling data. IE total 1+2+3=6. is it
possible in the total field to use data validation so if the total
is not equal to 6 then error?

I have tried this by establishing sum field totalling a1...a5 in A6
field, but when I go into input data into a1..a5 and it totals the
data validation on A6 doesn't provide an error message?

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