If variable F1 holds 143 (the thousands), F2 holds 012 (hundreds, tens and units) and F3 holds 5 (Single Decimal) then...

If F1>0 then
LCDOut #F1
If F2<100 then LCDOut "0"
If F2<10 then LCDOut "0"
endif
LCDOut #F2,".",#F3

This will ensure leasing zero's are surpressed, and appropriate zero's inserted (for example 100000.0 where F1=100, F2=0 and F3=0).