DateTime NOW()

[Jacque Scott]

I have a DateTime data type for one of my fields.  If an entry is being
INSERTed then I want the DateTime to be NOW().  I want this done
automatically and not have to set me SQL str to do this.  I have tried
to set the default as NOW() but it will insert
0000-00-00 ...  I don't want this, I want the current date.  I don't
want to use TimeStamp because I only want this done when there is an
INSERT not UPDATE.  
 
Does anyone have a suggestion?