Transferring a local variable in an interface into a process variable

Hi all,

I have a pickerFieldUsers field in my interface that I use to store a username into a local variable "local!userToTransferTo" which looks like this:

a!pickerFieldUsers(
label: "New Owner",
labelPosition: "ABOVE",
saveInto: local!userToTransferTo,
value: local!userToTransferTo,
required: true,
validations: {},
placeholder: "--Start typing officer name--"
),

The interface that contains this field is a Process Start form for a process model.  The process model [also] has a process variable of type "User" which is called "PVUserToTransferTo".

Back in my interface, I have a buttonWidget inside a buttonArrayLayout that looks like this:

a!buttonArrayLayout(
buttons: {
a!buttonWidget(
label: "Transfer",
style: "NORMAL",
saveInto: {
a!forEach(
local!dataGridSelection,
a!save(
target: null,
value: local!dataGridSelection
)
) /*,
a!save(
pv!PVUserToTransferTo,
local!userToTransferTo
)*/
}
)
},
align: "START"
)

There's actually two problems I'm trying to solve here.  The first problem - the one that I am asking at this time - is how to get the value that gets stored in local!userToTransferTo from the pickerFieldUsers object into the process variable PVUserToTransferTo where I can subsequently use the data in the rest of my process model.  When I un-comment out the code:

a!save(
pv!PVUserToTransferTo,
local!userToTransferTo
)

The form fails to render/compile, so this code is clearly wrong in some way.

Can someone advise how I get the value that is entered into the pickerFieldUsers object into a process variable that I can use in my process model?

thanks heaps,

David

In my process model properties