Add condition to formula
 

I want to add a condition to a formula so that the formula only returns a
result if the condition is met. Here is the formula:

=SUMIF(PO!$AI$24:$AI$1499,PO!$AI195,PO!$AN$24:$AN$ 1499)

If an additional cell PO!$AR195 contains the value "Yes" the formula will
return a result. If there is no value in PO!$AR195 then no result will be
returned.

Anyone know how to incorporate the above condition into the formula?

Many thanks if you can help.
Pat