Data Validation using ISBLANK with non-contigious cells

[Harry Flashman]

I have a range of non-contigious cells in Column A (named range -
Job1), and a range of of non-contigious cells in Column B (named range
- Job2).
How can I set up data validation to make it impossible to enter any
values in the range Job1 if there anything entered in any of the cells
in the range Job2.
I can use data validation for single cells easily enough. For example
if I want to stop people entering data in A1 if there is data in B2 by
using data validation/custom, formula =ISBLANK(B2). This works so I
thought I would extend it to the entire range. Thus I selected all the
cells in Job1 and applied data validation thus: =ISBLANK(Job2), but
this did not work. Then I realized that ISBLANK does not work with non-
contigous cells, so I tried messing around with COUNTA(Job2)=0 but
this did not work either.
Would anyone be able to help me please?
[Btw this is a simplified example, in fact these ranges appear on
separate worksheets.]

 

[Harry Flashman]

For the cells in Job1 I used the following data validation:
=COUNTA(Job2)=0
And I unticked the box that said "ignore blank"
It worked.

 

[Shane Devenshire]

Hi,

Most excel functions don't support non-contiguous ranges. That is the
problem here. In an empty cell enter the formula
=COUNTA(Job2)

Highlignt the Job1 range and choose Data, Validation, Custom and enter the
formula

=$D$1=0