How to add a new pop up widow to create requisition page?

Hi ,

We wanted to add a new pop up window in the "Create Requisition" page for the field "Agreement" with a message like for example "Please re-check the value" .

Attached screenshot shows the exact page and field where we are looking for. Once the Agreement value is provided a pop up window should come up with a message asking to recheck the value.

Could anyone assist me with steps how to achieve this?

Is it possible to achieve this?

Thanks

Sneha