VBA - 当单元格值= 1时打开一个msgbox

I need help with a very basic vba macro. When the value in A6 is equal 1 a msgbox needs to appear in the workstation. I developed the below code but the problem is that when I add any other information in the spreadsheet (for example, if I write "i love pizza" in B6) the msgbox will prompt again and I need it to prompt just one time, just when I set the value of A6 = 1. Could you please help me?I need help with a very basic vba macro. When t