Picklist Issue

hi team!

the problem is to change the value of picklist box using free flow scripting.

i have one picklist box in my form in that i have manually entered the value

now the problem is i have to link that pickup box to diff form to dynamic add the value

for that i use free flow scripting in without action and change the value script

for e.g

Presently

must have Type_Of_Work
    (
        displayname = "Type Of Work"
        type = picklist
        values = {"Desktop Call",   "Part Replacement",   "Full Day Engineer Call",   "Fresh Installation Call",   "Laptop Call",   "Shifting Call",   "Network Call",   "Router Call",   "PM Activity Call",   "Parts Repair Call",   "Server Call",   "Standby Parts",   "Printer Call",   "Monitor Call",   "Monthly Charges",   "Office Routine Work",   "Sales / Outward",   "Purchase / Inward",   "Payment Reminder",   "Part Repair Outsource",   "Scanner Call",   "Buyback / Inward"}
        sortorder = ascending
    )

need to change: (like lookup field)

must have Type_Of_Work
    (
        displayname = "Type Of Work"
        type = picklist
        values = formname.feildname
        sortorder = ascending
    )

previously i change the thing like this in previous version of zoho creator,
but now in zoho creator 3 it shows error "cannot change picklist type"

there is any way to change this field.