Need guidance for a Combo Box and Keystoke/Validate script

Question

Hello,
My goal is to have a combo box selection trigger and enter a value into a text field however the text field needs to be editable.  I want the combo box to determine a default value but changeable by the user if necessary.  Here is the script, I just don't know where to put it.
if (!event.willCommit) {
var M1Month = this.getField("Month 1 Pulldown").value; var M1Exp = this.getField("M1 Exp");
if(M1Month == "January") {M1Exp.value = "1/31/10"};
if(M1Month == "February") {M1Exp.value = "2/28/10"};
if(M1Month == "March") {M1Exp.value = "3/31/10"};
if(M1Month == "April") {M1Exp.value = "4/30/10"};
if(M1Month == "May") {M1Exp.value = "5/31/10"};
if(M1Month == "June") {M1Exp.value = "6/30/10"};
if(M1Month == "July") {M1Exp.value = "7/31/10"};
if(M1Month == "August") {M1Exp.value = "8/31/10"};
if(M1Month == "September") {M1Exp.value = "9/30/10"};
if(M1Month == "October") {M1Exp.value = "10/31/10"};
if(M1Month == "November") {M1Exp.value = "11/30/10"};
if(M1Month == "December") {M1Exp.value = "12/31/10"};
if(M1Month == " ") {M1Exp.value = ""};

Answer 1

I did not say to take out the line. You need to replace the "" (a null string),  with " " (a space).
But I would look at using the 'switch' statement that allows for a series of logical test and if none of those specific test has been passed takes a default action.
You need to put the script in the 'Custom keystroke script'.
if (!event.willCommit) {
var M1Exp = this.getField("M1 Exp");
if(event.changeEx == "January") {
M1Exp.value = "1/31/10";
} else if(event.changeEx == "February") {
M1Exp.value = "2/28/10";
} else if(event.changeEx == "March") {
M1Exp.value = "3/31/10";
} else if(event.changeEx == "April") {
M1Exp.value = "4/30/10";
} else if(event.changeEx == "May") {
M1Exp.value = "5/31/10";
} else if(event.changeEx == "June") {
M1Exp.value = "6/30/10";
}else if(event.changeEx == "July") {
M1Exp.value = "7/31/10";
} else if(event.changeEx == "August") {
M1Exp.value = "8/31/10";
} else if(event.changeEx == "September") {
M1Exp.value = "9/30/10";
}else if(event.changeEx == "October") {
M1Exp.value = "10/31/10";
}else if(event.changeEx == "November") {
M1Exp.value = "11/30/10";
}else if(event.changeEx == "December") {
M1Exp.value = "12/31/10";
}else{
// all other selections
M1Exp.value = "";
} // end not will commit
You will also need to use the 'event' object's 'changeEx' property.
If you do not need the selected text, by setting the export value to the expiration date your script could be:
if (!event.willCommit) {
this.getField("M1 Exp").value = event.changeEx;