Manual Running Total is not Resetting

I have a crystal report I wrote in Crystal 2008 off sql 2008.

For some reason, whenever a report group does not have a DPE value, it is picking up the DPE value from the previous record. Can someone help me solve this.

Thanks

In this report I have 4 groups;
Group 1 = Report Group
Group 2 = Grouping Summary Level 3
Group 3 =  Division Level
Group 4 = Group Sort

I have the reset formula in GH2.
Reset formula:
whileprintingrecords;
numbervar DPE;
""

I have the Summation being done in GH3
Summation Formula:
WhilePrintingRecords;
NumberVar DPE;

if {@Grouping Summary Level 3} = 'PAYROLL' THEN
       DPE := Sum ({@Month 3}, {@Grouping Summary Level 3})

I have the Display being shown in GF2
Display Formula:
whileprintingrecords;
numbervar DPE;  
DPE