Teach me for making up my own magic item...

So I gave out a magic dagger where when an attacker rolls 1 on the 1d4 attack it becomes a 4. My player currently is just manually adding +3 to the damage total when the damage is rolled as 1...when we remember to do this which I can't say happens 100% of the time in the heat of combat. Is there some sort of "IF imbedded statement" I can add to the dagger's attack such that 1 becomes a 4? Using the Wikis and forums I figured out Initiative macros, enlarged critical ranges and drop down windows for Sneak attacks- all super handy and  have improved the speed of our games. This seems a little harder to find guidance on the forums for. Thank you in advance from a Macro novice.

The easiest thing to do is to make a Rollable Table with the values 4,2,3,4 (or 2,3,4 with 4 double weighted), then roll that instead of a d4.  You could also roll [[{1d4+1,4d1}kl1]].  The 1d4+1 will have a range from 2-5, the 4d1 will always be 4, the kl1 (keep low 1) will pull the 5 down to a 4, giving a possible output of 2,3,4,4.

EDIT - ninja'd! You could make a rollable table with three entries. Values 2 & 3 have a weight of "1", and the entry for value 4 weighted to "2". Then, write a macro replacing the normal [[ 1d4 ]] with [[ 1t[TableName] ]]. This should give you the same probabilities as what you are describing.

Wow super fast answer. Much appreciated!