function onEdit(e){
var sheetName = "Debt"; //name of sheet to adjust formatting on
var currencyCol = 8; //column H
var amountCol = 6; //column F
var defaultFormat = "[$€]#,##0.00";
var currencyFormat = {"USD":"[Red][$$]#,##0.00",
"GBP":"[Red][$£]#,##0.00",
"EUR":"[Red][$€]#,##0.00"};
var r = e.range;
if(e.source.getSheetName()==sheetName && r.getColumn() == currencyCol){ //edits one cell at a time
var uf = currencyFormat[r.getValue()];
uf = uf?uf:defaultFormat;
r.offset(0,amountCol-currencyCol).setNumberFormat(uf);
}
}