Query on subsequent PO after initial PO

Hi Experts,

Our client has a requirement wherein items tagged as Initial stocks (UDF in OITM) will be created with PO and they need to track or an alert if this items has no subsequent PO created 90 days after first PO doc date. I will attach the query as alert to a certain user when the condition is met.

Our version is 8.81 PL09.

Many thanks.

Don