>>>>>If you have been able to locate the error portion, use something like
>>>>>

>>>>> substr(mstr,1 , pos-1) + '.' + substr(mstr, pos+1)
>>>>>

>>>>
>>>>
>>>>minimally faster and for my eyes easier to read...
>>>>

>>>> left(mstr, pos-1) + '.' + substr(mstr, pos+1)
>>>>

>>>
>>>

>>>STUFF(mstr,pos,1,'.')
>>>

>>
>>yupp, forgot that one, which is better
>
>would this not ADD the dot to whatever is already there??

No it won't - the 3rd parameter is the number of characters to replace/remove (the replacing string doesn't have to be the same length, so you can remove 2 and insert 23, or any other combination. Including zero, when it removes none - then it's an insert.