Data Validation to stop the use of commas and full stops

I am using Excel 2010 and trying to stop users of a spreadsheet from using full stops and commas in certain columns.

I was using data validation under data tools - allow custom then the following formula <>"."AND","

However, this does not allow the users to put any characters (special, numerical or letters) in the cell at all. Can anyone tell me a formula for this or point me in the right direction? Having looked at other posts I am slightly confused about VBA (do I need macros to use a formula to exclude special characters?)

Excel really is not my forte and I have spent almost all day googling a solution!

Thanks

Hello
Try the following Data Validation Custom Formula:

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Here I've applied it to a range of cells beginning in A1. This prevents the entering of commas and full stops in the selected range of cells. Hopefully!

Hope this helps.
DBY

Thank you so much - it works perfectly