Using Javascript to force tab to go to another field if the choice matches, what´s wrong?

I am using this script to force the tab to go to a specific field if the choice matches. However this also happens in several other fields in the document without this script. Can you help me to fix it?

if (this.getField("Details of Loan Drop").value=="Combination of 1ST & 2nd Mortgage (Explain Here)"){

this.getField("Texto25").setFocus();}

if (this.getField("Details of Loan Drop").value=="Combination of 1ST & 2nd & 3rd  (Explain Here)"){

this.getField("Texto25").setFocus();}