Cod in User Exit

Hi All,

I want to use below code  for formula variable with  user exit based on user entered value  from other variable 

DATA: ZI_T_VAR_RANGE LIKE I_T_VAR_RANGE WITH HEADER LINE.

IF I_STEP = 2.

CASE I_VNAM.

when 'ZVF_G_EXIT1'.

READ TABLE I_T_VAR_RANGE INTO ZI_T_VAR_RANGE WITH KEY VNAM = 'ZVPR3CUR'

                                                                                                                 IOBJNM   =  '0FISCPER3'.

if sy-subrc = 0.

clear l_s_range.

if ZI_T_VAR_RANGE-LOW = '3'.

move '-7.45' to l_s_range-low .

l_s_range-opt = 'BT'.

l_s_range-sign = 'I'.

CLEAR E_T_RANGE.

append l_s_range  to e_t_range.

endif.

endif.

I am not able to move "-7.45" into l_s_range-low , program is coming out of  if statement. I am not sure it going to work ,

Please let me know how to do that .

Thanks

Hari