Try the following:

create a variable of type string. Let's call it str_ExecSP.

Populate this variable with the following expression:

"EXEC dbo.proc_TEmptest " + (DT_WSTR,50) @[User::value1] + " , " + (DT_WSTR,50) @[User::value2]

Then use this variable in an Execute SQL Task. As SQLSourceType, select variable.