how to get values in multi select lookup field for each selected record?

how to get values in multi select lookup field for each selected record?

row.Mat_Purchase_Req is the multi select lookup field,
for each rec in row.Mat_Purchase_Req
{
if(row.Mat_Purchase_Req.size() = 1)
{
i = Material_Purchase_Requisition[ID == rec].Items_Required_for_Purchase1.ID;
i0 = Mat_Pur_Req_item_lookup[ID == i].Request_Qty_for_P_O;
}
if(row.Mat_Purchase_Req.size() = 2)
{
i1 = Material_Purchase_Requisition[ID == rec ].Items_Required_for_Purchase1.ID;
i11 = Mat_Pur_Req_item_lookup[ID == i1].Request_Qty_for_P_O;
}
if(row.Mat_Purchase_Req.size() = 3)
{
i2 = Material_Purchase_Requisition[ID == rec].Items_Required_for_Purchase1.ID;
i22 = Mat_Pur_Req_item_lookup[ID == i2].Request_Qty_for_P_O;
}
}
alert "" + i0 + "," + i11 + "," + i22 + "";
this is the script i am using to get the values of each record added in multi select field and it is written on a decision box user input named check. return values are in screen shot. My requirement is to get the alert of return values of 10, 20 and 30.
Please guide me how to choose the selected records separately. I dnt want to make a list and show alerts of values. so please kindly guide me accordinly.