A rough outline of the kind of script that would do this for a document with just one popup column:
Code:
property pTitle : "Set popup value of selected rows"
property pClear : "[CLEAR]"
tell application id "OOut"
tell front document
-- LOOK FOR A POPUP COLUMN
try
set colPopup to first column where type = popup
on error
display alert "No Popup column found"
return
end try
-- INVITE THE USER TO CHOOSE A POPUP VALUE (OR TO CLEAR THE VALUES)
set lstOptions to (name of enumerations of colPopup) & pClear
set varChoice to choose from list lstOptions with title pTitle default items item 1 of lstOptions
if varChoice = false then
return
else
set varChoice to first item of varChoice
end if
-- APPLY ANY CHOICE TO ALL THE SELECTED ROWS
if varChoice = pClear then set varChoice to missing value
set (value of cell id (id of colPopup) of selected rows) to (varChoice)
end tell
end tell