VBA so that each click generates a random character between A and Z in cell A1, and the number is displayed with a random font size in the range of 16 to 24 points.

can anyone help me out??

try using the ascii character map, ie chr(65) is A

find the table below
http://www.asciitable.com/

then use then randomize, and then the rand command to be able to pick a random character between the range that you require.

By memory it is rand(high-low)-low
try the below. (there might be a couple of errors as I haven't done VBA for a while)

randomize
  randomcharacter = rand(90 -65)-65
  range("A1") = chr(randomcharacter)