Jnix,
There are two ways to do this:
1. In the query:
Create a new column and make the field
BlahName:IIf([Field]= 0, "",[Field])
<"BlahName" is any name that you make up to recognize the field, "Field" is the name of the field in the table or query which you want to remove the zeroes from>
Basically, what the expression is doing is saying "if the field's value is equal to zero, then disply an empty string ("", in other words, BLANK), otherwise, show the value of the field."
Feel free to change the "" into any string that you would want to use to replace the zeros (such as "none" or whatever)
Then on the report, change the source of the control to this new field (don't forget to change the name of the control so you don't get an error)
2. In the report
Create a new control and set its souce to
IIf([Control]= 0, "",[Control])
<"Control" is the name of the control that you want to test for zeroes.>
Set the original control's visibility to "No"
I personally like to do these calculations in the query since it is then available to other forms/reports/queries that use it, but you might find that putting it on the report will improve performance.
Good luck,
Heather