Checking for a specific number in several ranges, popup if it exists (Most efficient way?)

Hi Guys,

I'm trying to make an efficient number checking macro that looks for the number 250 in certain cells/columns and if it exists to throw a popup.

Sheet 1:

Range("D2:J" & LastRow)
Range("L2:M" & LastRow)

Sheet 2:

Range("E15:P" & LastRow)

LastRow is defined by Column A

Filters? For loops? Arrays? or Search/Find?

I'd greatly appreciate some snippets of code to do this in the most efficient way.