Disable lookup autofill

Hi

This may sound weird.

I have a lookup table, using which I lookup user name and populate their location on the main sheet (using VBA code).

For names missing in the lookup table, I get #N/A, which is expected.

Next, I loop through all #N/A's on the main sheet, and add their corresponding user names in the lookup table.

Here, I want to stop my program, and pop up a msgbox to add locations for user names newly added in the lookup table.

But, as soon as the names are added to lookup table, their locations are updated as 0 on the main sheet.
I think this happens due to lookups refreshing automatically, and substituting missing locations with zero's. (Remember, user has not yet got a chance to update these lissing locations in lookup)

Is there a way to stop this lookups refresh until user manually updates loctions and clicks a button?

I will try to create a sample sheet with this scenario, and upload it later today, but meanwhile, if anyone has any solution, I will appreciate it very much.

tia
Ajay