You are trying to combine 2 actions. You need to do this in 2 steps.

Try it this way

Create a formula

If {Table.fieldA} <> 'I' then

1

else

0

Save the formula

Drop the formula onto the report

Right click the formula field on the report

Click INSERT --> SUMMARY

Set it for a SUM

Put it in the report footer

You can then delete the formula field from the report

mlmcc

Try it this way

Create a formula

If {Table.fieldA} <> 'I' then

1

else

0

Save the formula

Drop the formula onto the report

Right click the formula field on the report

Click INSERT --> SUMMARY

Set it for a SUM

Put it in the report footer

You can then delete the formula field from the report

mlmcc