Thanks Marvin. I have played with your example and it does indeed work. I don't understand how your code works, unless its checking every entry made into excel by the user? i.e. it does not appear to be explicitly checking cell C13?

Suffice to say I cannot get it to work in my sheet, so I better start reading up.

Also I am going to need a fair number of these triggers in the sheet depending on what people choose in the drop down box will determine what rows show or do not show.

I was able to do this in another sheet with true or false statements linked to tick boxes, but they are not appropriate in this situation