RobotFramework - keyword assign multiple variables, how to execute it only if condition?

im facing this problem like a noob. It should be easy, but i dont find de way.

I have a Keyword that returns multiple values, reading from a file. I use it to set some variables like this:

${A} ${B} ${C} ${D} ${E} ObtainVariablesKeyword

Where ObtainVariablesKeyword has some code and finally:

[Return] ${A} ${B} ${C} ${D} ${E}

The thing is sometimes data is not in a file, instead user write it., So i'd like to run first example row only IF CONDITION.

Does anybody know how?

Run keyword if CONDITION KEYWORD, does not allow to put variables after condition, cause it waits for a keyword...

Thank You very much in advance.