Please help with (the script). Necessary to multiply the two cells. The first is the QTY (set by hand). The second cell is given a choice between four ranges.

OK, that's what I thought, but your example did not show the same results, which was confusing. Also your field names don't seem very consistent. I suggest you rename them to something like Qty1, UP1_1, UP1_2, UP1_3, UP1_3 and Total1.

Let's say that's the case. Then you can use this custom calculation script for Total1:

var qty = Number(this.getField("Qty1").value);
var unitPrice = 0;
if (qty>=1 && qty<=50) unitPrice = Number(this.getField("UP1_1").value);
else if (qty>=51 && qty<=999) unitPrice = Number(this.getField("UP1_2").value);
else if (qty>=1000 && qty<=2499) unitPrice = Number(this.getField("UP1_3").value);
else if (qty>=2500) unitPrice = Number(this.getField("UP1_4").value);
event.value = qty*unitPrice;