sometimes i use msgbox just for debugging

you can use this in a very simplistic form:

msgbox "any text here"

or

msgbox any_variable_here


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but for your question, this might work:

if msgbox("Do you want to continue?", vbYesNo, "My Program") = vbYes then
msgbox "you chose YES" 'put the code for 'yes'
else
msgbox "you chose NO" 'put the code for 'no'
endif