Button Activation in Display Taxes as shown in attachment in PO

Dear Experts,

I have requirement from Client to activate the Next button, Previous button i.e. all 4 buttons we see in Display Taxes Screen in PO, i.e. In Invoice tab at item level of PO, when we click on Taxes button, New Screen appears of Display Taxes, there we can find the 4 buttons just below Display Taxes header, I have searched a lot but did not find any relevat reply, Need Experts opinion regarding this, Any Note will be also helpful.Please look at attachment for the requirement,

Regards

Priya Singh