>>>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