find the largest value in column, put in a cell

[Guest]

If value in cell a1 = 1 through 149, display "0" in a2
If vallue in cell a1 = 150 or greater, display actual value of a1, in cell a2

 

[Paul Lautman]

If value in cell a1 = 1 through 149, display "0" in a2
If vallue in cell a1 = 150 or greater, display actual value of a1, in
cell a2

In A2:
=IF(A1<150,0,A1)

 

[davesexcel]

If value in cell a1 = 1 through 149, display "0" in a2
If vallue in cell a1 = 150 or greater, display actual value of a1, in
cell a2

Whoops!!,
Might have the wrong question here,
I will answer your Title question,

=MAX(A2:A8)

this will give you the max number in the range A2:A8