[Aetae]

document.onmousedown = function(e){
  e = e? e.target : event.srcElement;
  if(e && e.id && e.tagName === 'INPUT' && e.type === 'submit' && /_[^_]+_btnMakePurchase/.test(e.id) ){
	(
		document.getElementById(e.id.replace(/_([^_]+)_btnMakePurchase/,'_$1_txtPurchasePrice')) ||
		document.getElementById(e.id.replace(/_Make([^_]+)_btnMakePurchase/,'_$1_txtPurchasePrice'))	
	).value = document.getElementById(e.id.replace(/_[^_]+_btnMakePurchase/,'_upd_small')).innerHTML
  }
}