I don't have Microsoft Outlook, so I can't test my suggestions out, but I imagine you could get every signature whose name is sigName, then decide if you want to just delete them all and make a new one, or keep one, edit it, and delete the rest. I'm obviously working on the assumption there could be anywhere between 0 and N signatures sharing one name that have accumulated over time. From this standpoint, I'd say that deleting them all and making new one would be easiest coding wise, provided Outlook lets you delete a list of signatures the way, say, Finder lets you delete a list of files in a single command:
tell application "Microsoft Outlook" to delete every signature whose name is sigName
If it doesn't, you would have to construct a repeat loop and delete them one by one:
tell application "Microsoft Outlook" to repeat with S in ¬
(every signature whose name is sigName)
set S to the contents of S # (dereferencing)
delete S
end repeat
If you decide you want to keep one and edit it, then:
tell application "Microsoft Outlook"
set S to every signature whose name is sigName
if (count S) is 0 then
# make new signature
else
set [R] to S
delete the rest of S
set the content of R to the sigContent
end if
end tell
If delete the rest of S doesn't work, a repeat loop again will let you delete items 2 onwards individually, and keep just the first item to edit.
I'm sorry I can't test this for you, but it's at least an indication of how to go about trying to do it.