Changing the duration of a pulse in PSPICE
An example of usage is:

VLIGHT Node1 Node2 EXP(0V 400V 0uS 20uS 40uS 20uS)

with the format EXP( V1 V2 [Td1 [Tau1 [Td2 [Tau2]]]])

The EXP form causes the the voltage to be V1 for the first TD1 seconds, then the voltage decays exponentially from V1 to V2 with time constant Tau1.  The delay lasts Td2-Td1 seconds.  Then the voltage decays from V2 back to V1 with time constant of Tau2.

You state that the pulse duration must exist for 110-120 us but you don't define what the definition of pulse duration is.  Is it \$e^{-1}\$? or is it 90% -> 10% ?.  When dealing with exponentials, 6 time constants is considered to be fully settled.  So in your case if Tau1 = Tau2 and you want it fully settled then Tau1=Tau2=10 uS -> 60 us to settle up and 60 us to settle down for a total of 120 us.