Anyone can help me on excel QUEUE vbA?

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pic 1 position of BP and TP
BP(base pointer), TP(top pointer) TP always up 1 level from BP

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Pic 2
when click the button Push, will add 1 event number，and TP will also up 1 level

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Pic 3
When research the max， msgbox will appear Queue Full.

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when click button pop， will start delete from the base. and the entire column number & TP will moving down 1 level. Finally when the TP pointer back to the orginal place，msgbox appear queue empty