can someone give me an idea

If I have a constant variable and I want to change text values in it with other variables, how can I do that.

LTEXT = "Testing &1 &2 &3"

L1 = "Test1"

L2 = "Test2"

L3 = "Test3"

*ABAP CODE HERE, replace &1 with L1, &2 with L2, and &3 with L3 and store in LTEXTREP

LTEXTREP now equals "Testing Test1 Test2 Test3"