You can tell Macro Scheduler only to resolve variables that are contained within % symbols and to leave anything else as literals by setting the VAREXPLICIT variable to 1:

Let>VAREXPLICIT=1

The default is 0 and will cause default behaviour as described above - i.e. Macro Scheduler will look at any parameter to see if it is a variable. If a variable with that name exists, the value assigned to that variable is used, otherwise just that literal value is used.  Setting VAREXPLICIT to 1 stops this behaviour and tells Macro Scheduler only to resolve a variable if it is contained within % symbols.  E.g.

Let>VAREXPLICIT=1

Let>Name=Fred

Send>Name

Send>%Name%

In this case the first Send> command will send the literal 'Name' and the second would send the value 'Fred'.  In the following example, which is the default behaviour, both Send> commands would send the value 'Fred':

Let>VAREXPLICIT=0

Let>Name=Fred

Send>Name

Send>%Name%