replace the comma separator to a dot and dot to a comma at the same time

I have a set of data in Column A1 to A100

i need a macro to replace the comma separator to a dot but at the same time, dot separator to a comma separator ?
but if the number has only comma separator or only dot separator no action should be taken

for example
1,765.12 should be like 1.765,12

but
if the number contains only dot or only comma no action should be taken
for example

1765,12 number should not be changed




please help