Please help me in a function

If value already stored in my udf then this function working perfect but
if i create a voucher then error showing

Code:

[#Form    : Sales Color]
    On    : Form Accept    : Yes    : Form Accept
    On    : Form Accept    : Yes    : Call        : Vch Update Fun    :@@CurrVoucherID
   

[System    : Formula]
    CurrVoucherID    : $$String:"ID:"+$$String:$MasterID

[Function    : Vch Update Fun]
    Parameter    : MSTID : String
    Variable    : IsDeleteYN : Logical    : No
    Variable    : NumItems :Number
    Objects:Voucher :##MSTID
   
    Action:010 : Start Batch Post
    Action:020 : SET TARGET
    Action:030 : Set Object
   
    Action:050 : Walk Collection : All Inventory Entries
    Action:051 : SET TARGET:InventoryEntries[$$LoopIndex].
    Action:052 : Walk : myudfs1
    Action:053 : SET TARGET:myudfs1[$$LoopIndex].
    Action:054 : Set    : IsDeleteYN  : if $IsRettktEnable=No Then Yes else No

    Action:400 : If:##IsDeleteYN=Yes
    Action:479 : Set    : NumItems : $$NumItems:myudfs6
    Action:482 : While    : NOT ($$IsEmptyCollection:myudfs6)
     Action:483 : DELETE COLLECTION OBJECT    : myudfs6    : 1    : Yes
     Action:485 : End While
    Action:490 : End If
    Action:511 : End Walk
    Action:531 : End Walk
    Action:630 : SET TARGET  : ..
    Action:640 : ACCEPT ALTER
    Action:680 : End Batch Post

 

if you are creating use different function
as there will be no voucher to query using masterid

For create, syntax will be
...
NEW OBJECT : Voucher
...


refer this What are Procedural-Object/Collection Related Actions in TDL? | TallyHelp (tallysolutions.com)