string that contains Items Included in bill

I want a string that contains

item + qty + amt

item1 10pcs 10000 item2 5pcs 500

and as go on
for the all item included in bill

 

Create System Formula that Will Calculate Qty and Amount
Example:
[System:Formula]
Qty:$ActualQty
Amt:$Amount

Create a field that will show the value and convert everything in String
Example:
[Field:Example]
Set as: $$String:$StockItemName + $$String@Qty + $$String@Amt

 

I try but Not working please help me how can i use feild in string
here is code I used

[#Form: Sales Color]
Add : Button : WhatsApp
On : Form Accept: @@IsSales : CALL : onformaccept

[Button: WhatsApp]
Option : SalesjayA : $VoucherTypeName="Sales"

[!Button: SalesjayA]
Key : Alt + W
Action : Browse URL : "whatsapp://send?Phone=" + @@mobileno+ +"&text=" + @@List


[System: Formula]

Qty:$ActualQty
Amt:$Amount

[Field:List]
Set as: $$String:$StockItemName + $$String@Qty + $$String@Amt

[Functionnformaccept]
10 : QUERYBOX : "Send Whatsapp msg" : Yes:No
20 : IF : $$LastResult
30 : CALL : whatsappstring
40 : ENDIF

[Function: whatsappstring]
00 : Browse URL : "whatsapp://send?Phone=" + @@mobileno+ +"&text=" + @@List

 

It will not work because I gave you example not solution...You have to learn from example

 

I don't want to display field I want collection of all StockItemName in string
how can I do that ?

 

Sir, I tried but I didn't understand. sir can you explain in brief please sir