Dynamic Stamp with multiple input from option buttons to be filled into the checkbox!

I have an error :

TypeError: this.getField(...) is null

115:App:Calculate

if(event.source.forReal && (event.source.stampName == "#pfP__PjJ7SwG7RRWsGspWA"))

{

if ("ok" == app.execDialog(DiaBox))

{

this.getField("Approved - Submit Final Copies").checkThisBox(0, DiaBox.bChk1);

this.getField("Approved as commented - Resubmit").checkThisBox(0, DiaBox.bChk2);

this.getField("Not Approved - Resubmit").checkThisBox(0, DiaBox.bChk3);

this.getField("Cleared for Manufacture").checkThisBox(0, DiaBox.bChk4);

this.getField("For Information").checkThisBox(0, DiaBox.bChk5);

var cMsg = DiaBox.byName;

event.value = "Remarks # " + cMsg;

event.source.source.info.exhibit = cMsg;

}

}

var DiaBox =

{

result:"cancel",

DoDialog: function(){return app.execDialog(this);},

bChk1:true,

bChk2:false,

bChk3:false,

bChk4:false,

bChk5:false,

stredt1:"",

initialize: function(dialog)

{

var dlgInit =

{

"Chk1": this.bChk1,

"Chk2": this.bChk2,

"Chk3": this.bChk3,

"Chk4": this.bChk4,

"Chk5": this.bChk5,

"Name": this.stredt1,

};

dialog.load(dlgInit);

},

commit: function(dialog)

{

var oRslt = dialog.store();

this.bChk1 = oRslt["Chk1"];

this.bChk2 = oRslt["Chk2"];

this.bChk3 = oRslt["Chk3"];

this.bChk4 = oRslt["Chk4"];

this.bChk5 = oRslt["Chk5"];

this.byName = oRslt["Name"];

},

description:

{

name: "Stamp",

elements:

[

{

type: "view", elements:

[

{

type: "view",

char_height: 10,

elements:

[

{

type: "static_text",

item_id: "stat",

name: "Please select the review category:",

width: 152,

height: 23,

char_width: 15,

alignment: "align_fill",

font: "dialog",

},

{

type: "radio",

item_id: "Chk1",

group_id: "rado",

name: "Approved - Submit Final Copies",

},

{

type: "radio",

item_id: "Chk2",

group_id: "rado",

name: "Approved as commented - Resubmit",

},

{

type: "radio",

item_id: "Chk3",

group_id: "rado",

name: "Not Approved - Resubmit",

},

{

type: "radio",

item_id: "Chk4",

group_id: "rado",

name: "Cleared for Manufacture",

},

{

type: "radio",

item_id: "Chk5",

group_id: "rado",

name: "For Information",

},

{ type: "edit_text",

item_id: "Name",

height: 23,

char_width: 20,

char_height: 10,

alignment: "align_center",

name: "Enter Initials",

}

]

},

{

type: "ok_cancel",

},

]

},

]

}

};